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hep-th/0206175
Exciting AdS Orbifolds
Emil J.Martinec 1and Will McElgin 2Enrico Fermi Inst.and Dept.of Physics University of Chicago 5640S.Ellis Ave.,Chicago,IL 60637,USA Abstract The supersymmetric (AdS 3×S 3)/Z N orbifold constructed by the authors in hep-th/0106171is shown to describe AdS fragmentation,where ?vebranes are emerging from the F1-NS5background.The twisted sector moduli of the orbifold are the collective coordinates of groups of n 5/N ?vebranes.We discuss the relation between the descriptions of this background as a pertur-bative string orbifold and as a BPS state in the dual spacetime CFT.Finally,we attempt to apply the lessons learned to the description of BTZ black holes as AdS 3orbifolds and to related big crunch/big bang cosmological scenarios.
1Introduction and Summary
Much interesting structure of string theory has been revealed through the investi-gation of its asymptotically AdS backgrounds–the precise counting of black hole microstates[1];the matching of low-energy black hole emission/absorption spec-
tra between string theory and supergravity[2,3];the UV/IR connection[4];and spacetime topology changing transitions[5]-[7],to name but a few.The overarching
idea encompassing all of these results is the duality between quantum gravity and a holographically dual conformal quantum?eld theory[8].
The AdS3example has?gured prominently in these discussions;it arises as the
near-horizon geometry of n1strings and n5?vebranes.In addition to the above list of results,it has also proved a fruitful ground for exploring additional issues,such as the black hole information paradox(see[?]-[12]for a few examples),and the role
of singular conformal?eld theories[13].
One distinctive feature of AdS3is that the supergravity side of the correspon-
dence admits a perturbative string description at points in moduli space with van-ishing RR?elds[14],giving one access to more than just the low-energy supergravity spectrum and dynamics on the‘bulk’side of the correspondence.Another is that the
current algebraic nature of the conformal symmetry provides more powerful tools in the analysis of the‘boundary’theory–in this case a sigma model on the moduli
space of instantons[15,16,17].
Given the degree of control one has over both sides of the correspondence for AdS3/CF T2,one may ask whether it is possible to study black hole physics while
having simultaneous control over both a bulk and boundary description of the dy-namics,for instance to see the‘long string modes’describing black hole states[18] in a description that also has control over local physics in the bulk,such as that
of[14].It was with this goal in mind that the authors began a study of AdS3×S3 orbifolds in[19],in part because of the naive interpretation of the AdS3or BTZ
black hole[20,21]as an orbifold of global AdS3spacetime.
The orbifold procedure is a useful way of generating new backgrounds from solv-able examples.Where the orbifold operation takes the theory seems to be strongly example-dependent.For example,a chiral Z N orbifold of the S3has the interpreta-tion of adding KK monopole charge to the background[22].The e?ect on the dual CFT of this orbifold operation is not known(see[23]for a discussion).
In[19],it was shown that the bulk orbifold(AdS3×S3)/Z N(by opposite Z N rotations in both S3and in the spatial directions of AdS3)yields a BPS state in the same spacetime CFT that describes the original global AdS3spacetime as its SL(2)invariant vacuum state.Reasons for considering this orbifold include(i)the technology for time-independent orbifolds is well-understood;and(ii)naively the geometry approaches the extremal BTZ black hole threshold from below as N→∞, so one might hope to have a situation where there is some degree of control over both geometry and black hole degrees of freedom.
In this work,we examine the latter construction in more detail,in particular
we?nd in section2precisely which among a large degeneracy of BPS states is being described by the bulk orbifold.It will turn out that the con?guration being described is that of N groups of n5/N?vebranes near the point where they emerge onto the Coulomb branch of their moduli space3.We further give an interpretation of the various excitations of the orbifold in section3–especially the twisted sectors, where the twisted sector moduli are shown to describe the relative separations of the?vebranes.
It also turns out that there is a remarkable parallel between the description of the rotational orbifold in the bulk perturbative string theory and the description of the twist vertex operators in the dual boundary CFT that create the corresponding BPS states from the SL(2)invariant https://www.doczj.com/doc/242571725.html,ly,the twist operator correlation functions have the same geometrical description in terms of the vacuum-to-vacuum amplitude on a branched cover of the Riemann sphere(the Euclidean AdS3bound-ary),as the bulk orbifold does in terms of its branched cover onto the global AdS3 spacetime!
After a brief comment on related?vebrane backgrounds in section4,we turn in section5to a discussion of the AdS3black hole geometry as an orbifold[20,21]. After reviewing the geometry of the identi?cation,we discuss the nature of the vacuum and in particular its behavior near the black hole singularities.
As a classical geometry,the eternal AdS3(BTZ)black hole is a quotient of the AdS3geometry by an element of the SL(2,R)×SL(2,R)isometry group that roughly speaking acts as a boost rather than a rotation.Thus,a freely falling observer experiences a geometry that near the singularity looks like a sort of Milne universe.Such geometries have been periodically identi?ed as interesting subjects for investigation,both in the context of perturbative string theory and in quantum cosmology[25]-[40].The group action identi?es the boundary of AdS3in such a way that the intersection of the black/white hole singularities with the boundary are again locally Milne singularities,now in the1+1dimensional CFT on the Lorentzian cylinder which is the conformal boundary of AdS3.If one considers SL(2,R)rather than its covering space,there are four such singularities(two if one further identi?es to the Poincar′e patch P SL(2,R)).
The advantage of an AdS3based example is again that one may be able to bring to bear both a perturbative bulk(string)description of the BTZ orbifold[25, 26,27,35,36,37,39]as well as a two-dimensional boundary CFT description. As discussed above,in matching the two dual descriptions,one must overcome the obstacle that it is not always known how the orbifold procedure a?ects the boundary theory.This is especially true when we abandon orbifold actions that preserve su?cient supersymmetry to guarantee some amount of nonrenormalization of the background,since we lose control over what properties of tree-level string theory are
maintained in the full nonperturbative quantum state;there is no guarantee that string perturbation theory is an accurate guide to the exact geometry.Quantum corrections could completely invalidate the picture of the geometry as an orbifold, i.e.as something that can be covered onto the global AdS3geometry.Nevertheless, we proceed under the assumption that states in the boundary theory which respect the appropriate discrete symmetries will possess the same basic characteristics as the Kruskal vacuum of the BTZ geometry,and attempt to deduce some of their properties.4If this assumption proves incorrect,then one cannot characterize the BTZ black hole as an AdS3orbifold.
A persistent question in the AdS/CFT correspondence has been how to describe propagation into the black hole singularity within the framework of the dual CFT;
a related source of confusion is what it means to propagate through the horizon of the extremal brane geometry according to the global time rather than the Poincar′e time naturally related to the brane Hamiltonian(see for example[10]).A funda-mental issue is how to treat the intersection of the horizon(and/or the singularity) with the conformal boundary.In fact,it is generally true that the outer horizon, inner horizon,and singularity of any BTZ black hole all coincide at the boundary of the AdS covering space.The transformation between the global and Poincar′e coordinates,or between global and BTZ Kruskal coordinates,has singularities at these points;blithely adding the singular locus to the conformal compacti?cation of the Poincar′e patch or the Kruskal boundary is not always justi?ed.In the present context,the question becomes whether the states in the boundary theory that re-spect the(extremal or nonextremal)BTZ identi?cation have a sensible description in the Hilbert space of eigenstates of the global time,so that one can make sense of propagating them through the Milne singularities.A reasonable prescription for dealing with such singularities in1+1dimensional CFT would go a long way toward justifying recent speculations about cosmological singularities by providing them with an interpretation in a fully quantum mechanical realization of gravity,via the interpretation of the CFT as the boundary dual to asymptotically AdS quantum gravity.
We will?nd that the stress tensor of the required CFT state diverges rather badly along the light cones emanating from the singular locus on the boundary, presenting a di?culty for the orbifold characterization of the black hole,and asso-ciated cosmological models.Such a divergence might be regarded as an instance of the generic divergence of stress tensors on Cauchy horizons(c.f.[41]and references therein).
We conclude this introduction with a comment on the apparent diversity of presentations of the BTZ black hole.There are by now many descriptions of CFT states purportedly dual to the black hole–the thermal state in the Hilbert space
H of the CFT;the entangled state in H?2suggested by the Kruskal geometry; states formed by collapse of energetic states in supergravity;and the hyperbolic orbifold.Are they all the same black hole geometry?Our view on this issue is that they are not.They are distinguished by the history along the entire spacetime boundary which they possess.For instance,a generic state in the thermal ensemble, or one formed by the collapse of energetic probes dropped from the AdS boundary, employ a single CFT Hilbert space H and describe a spacetime with one asymptotic boundary;while the correlated state in H?2of[12]describes a spacetime with two disjoint asymptopia.Any set of observations made on a single asymptotic boundary in any of these examples will?nd what semiclassically looks like a black hole.There is a certain arti?ciality to the AdS/CFT correspondence when viewed cosmologically, in that there is an external agent who sets up the‘universe’under consideration. The generic high energy eigenstate state in H will be approximately thermal in its properties,and does not arise from a collapse process,but still looks like a black hole.The universe one‘creates’may have one asymptotic boundary,as in the case of the thermal CFT state;or it may have two,as in the case of the entangled state of the Kruskal extension(it may also have many,or possibly none[28]!).It may not be possible to detect the full geometry on the basis of experiments available to any single observer,but that does not invalidate the cosmology until and unless one can develop criteria to eliminate these more exotic examples with multiple holographic screens.This observation may also have consequences for de Sitter cosmology,where the supposition of a holographic dual containing only a horizon area’s worth of states assumes that there is no part of the world holographically inaccessible to a given observer.Finally,the ability to cover cosmologies with closed spatial geometry onto global AdS spacetime may indicate the presence of non-obvious and/or non-local observables(c.f.[40]),whose apparent lack has long been a stumbling block in understanding closed quantum cosmologies.The answer to these questions bear upon whether intial conditions with cosmological past horizons are admissible,and if so,what data describes the correlations between various causally disconnected domains.
Note added.While this manuscript was in its?nal stages of preparation,we learned of related work[42]on the conical geometries of sections2and3.
2Rotational orbifolds and U-duality
To begin,we consider the rotational orbifold(AdS3×S3)/Z N.Our goal is to establish the relation of the orbifold geometry with a speci?c BPS state of the dual spacetime CFT.By U-duality,the BPS charges of the n1fundamental strings and n5?vebranes wrapped on T4×S1can be mapped to momentum and winding charges of a fundamental string on the S1;the BPS con?gurations of such a string are well-known to correspond to the di?erent ways that one can satisfy the level-matching constraints by exciting left-moving oscillators while keeping the right-movers in their
ground state.Lunin and Mathur[43,11]have worked out the relation via U-duality of the metric sourced by such a fundamental string carrying winding and momentum on a circle(call it the?x5direction)to the corresponding geometry of the D1-D5or equivalently the F1-NS5system;let us recall their analysis.
The chain of dualities in question is
?→P-D4T678?→P-D1S?→P-F1(1) F1-NS5T5
?→P-NS59/11?ip
(we assume that the NS5brane is additionally wrapped on a T4along the6789 directions).The BPS charges carried by the U-dual fundamental string are thus n w=n5and n p=n1.As discussed in[44],the P-F1duality frame is the appropri-ate low-energy description for the very-near horizon physics(i.e.ultra-low energy perturbations),and so it is appropriate to consider this U-duality frame for the purpose of understanding the structure of the vacuum and its low-lying excitations.
Level matching on the string requires a left-moving oscillator excitation of level n1n5.The general class of such states is(referring dimensions to the string scale?s, which will be suppressed)
?x i(τ+σ)= m a m m e im(τ+σ)+c.c
n1
?x5=
√
N m.There are of order exp[2π
=c
24
5Recall that in the F1-NS5duality frame,the AdS scale is?=√
where T 30is the left-handed S 3angular momentum,and c =6n 1n 5.The right-moving quantum numbers are identical.-1
01
X
5
01
X 1-10
1X 2
Figure 1:The spatial con?guration of the U-dual string source for n 5=50,N =1,corresponding to global AdS 3×S 3.The ?x 5direction is periodically identi?ed to make an n 5times wound string.Smearing the source along ?x 5generates a ring source in the ?x 1-?x 2plane.
The SO (4)=SU (2)×SU (2)angular momentum along the transverse directions 1234in the system is T 30=12(M 12?M 34).When the F1-NS5system is mapped to the P-F1duality frame,angular momentum (?1
2)
for each oscillator describes a string rotating in the 1-2plane.The total angular momentum of the state (3)is thus T 30=ˉT 30=n 1n 5/2N in R sector conventions,or 1
?Rn 5(?t +?x 5)
?x 2≡?F 2(?t +?x 5)=a sin N n 1n 5/N .Plots of the spacetime con?guration of such a
source in the P-F1duality frame are shown for global AdS 3×S 3,N =1,in ?gure 1;and a naive con?guration for N >1is shown in in ?gure 2.Note that the locus of the string in spacetime is traversed N times as σgoes from zero to 2π.
-1
01X
501
X 1-1
1
X 2
Figure 2:The spatial con?guration of a U-dual string source for n 5=50,N =5,related to (AdS 3×S 3)/Z 5.The strands are separated slightly for visualization purposes.The actual source for the orbifold puts the strands at ?nite separation.
The geometry sourced by this string con?guration is
ds 2=?H
?1 ?d ?t 2+d ?x 25+?Kd ?v 2+2?A i d ?x i d ?v +d ?x ·d ?x +dy ·dy B ?u ?v =?G ?u ?v =1
|?x ??F |2,?K =n 5|?F
′|2|?x ??F |2.(8)
In order to be able to simply U-dualize this source con?guration to the F1-NS5duality frame,it is necessary to smear the source along ?x 5.6De?ning
?z =?x 1+i ?x 2,?w =?x 3+i ?x 4,(9)
one ?nds after averaging the source over ?x 5that
?H
=n 56
The smearing operation is a linear operation on harmonic functions,hence preserves the prop-erty of solving the supergravity equations of motion.
?K=n1
n1n5a y2
f0
(10)
?A 2=
√
|?z|2
|?z|2+|?w|2+a2?f0
n1n5a y4
f0
B4=√
|?w|2
|?z|2+|?w|2?a2?f0
n1n5/N one recovers the(AdS3×S3)/Z N
orbifold geometry
ds2/?2=?(r2+a2
r2+a2
√√
n1n5r2+a2sinθe iχ
w=√
N2(r/a)2dx25+(θ?π/2)2(dψ?
1
(a standard form of the ALE metric at the orbifold point results from the substitution r/a =ρsin α,θ?π/2=ρcos α).So indeed,(AdS 3×S 3)/Z N corresponds to the dual source (6).
Since the dual string source consists of N strands which coincide in spacetime,the N -wound source can split into N separate sources at no cost in energy.These N strands each carry n 5/N units of winding,and a fraction n 1/N of the momentum 7.The N separate strands of P-F1source yield a moduli space of multicenter solu-tions,obtained by replacing the harmonic functions and gauge ?elds (11)by their multicenter counterparts
?H =n 5
f 0,α
?K =n 1
f 0,α
(16)
?A 1=?√N N α=1(y 2?y 2,α)
f 0,α
?A 2=√N N α=1(y 1?y 1,α)
f 0,α
f 0,α=
(|?z ??z α|2+|?w ??w α|2+a 2)2?4a 2|?z ??z α|2 1/2.One can show that,expanding the metric near the sources for separations |z α|,|w α|?
a ,the metric assumes the ALE form ds 2/?2=V ?1( x )(dx 5+ ω·d x )2+V ( x )d x ·
d x V ( x )=√Na N i =1
| x ? x i |?1,dV =?dω;(17)
here x is the three-vector of coordinates out of the directions 1234that is locally transverse to the ring source.In other words,V is the near-source limit of (HK )1/2,
and ωis the near-source limit of B in the appropriate three directions.The fourth
parameter of the multicenter solution is the separation of the sources from one an-other in the angular direction along the ring,or equivalently in the T-dual coordinate ?x 5.Upon smearing over ?x 5,these solutions separated along this angular direction are no di?erent from the single center solutions (11);however,string dynamics on (AdS 3×S 3)/Z N knows about this deformation –for instance,in the analogous sit-uation of string theory on R 4/Z N ,this deformation amounts to adjusting the NS
B-?ux through the N?1collapsed cycles of the ALE space,while maintaining the conical metric of R4/Z N.Thus,the(AdS3×S3)/Z N orbifold spacetime yields a variation on the well-known duality between ALE spaces and NS?vebranes[46].
The couplings to the twisted sector marginal operators[19]
ΣSL(2) q ΣSU(2)
N?q
,q=1,...,N?1(18)
of the string theory orbifold(AdS3×S3)/Z N should therefore be identi?ed with the moduli deformations of the multicenter solution(the four overall translation modes decouple in the near-horizon limit).Indeed,in the?at space limit k→∞these operators become twisted moduli of the R4/Z N orbifold CFT.The twist oper-ators(18)lie in the(2,2)representation of the global SU(2)×SU(2)R-symmetry, i.e.they are a vector in the R4transverse to the?vebranes(the operators(18)are the bottom(?,?)components of the multiplet).The operators(18)are products of parafermions from the SL(2)and SU(2)current algebra theories,and thus iden-
tical to the moduli of the(SL(2,C)
U(1))/Z N sigma model of[47]describing a
decoupling limit of slightly separated?vebranes;in the latter context,the deforma-tions are the operators that move?vebranes in their transverse space(see[47]and section4below).In the?vebrane sigma model,it is known that at?nite distance in the moduli space one?nds singular worldsheet theories corresponding to points where two or more?vebranes come together.Therefore it is unreasonable that the ?vebrane sources should coincide as in?gure2,since this should yield a singular worldsheet CFT.
The point described by the coset model has the?vebranes arranged in a Z N symmetric fashion along a two-dimensional plane.This strongly suggests that we should interpret the magnetic Z N symmetry of the orbifold theory in terms of a Z N symmetric arrangement of the unsmeared sources around the ring of?gure2,see ?gure3.The separation of the N strands at the orbifold point is in a coordinate along which the source has been smeared,so the deformation along that direction will be invisible in the geometry,just as in the B-?eld deformation of R4/Z N.
In particular,we see that at?nite distance in the moduli space,where strands of the dual P-F1strings come together,the worldsheet CFT becomes singular.The point where all the strings come together is the con?guration depicted in?gure2; we now see that this con?guration lies at a singular point in the moduli space, where perturbative string theory breaks down.The fact that it takes?nite energy above the AdS vacuum to reach a singular CFT is consistent with the fact that the strands of the dual string are separated and have no moduli in the global case N=1 depicted in?gure2;it thus takes?nite energy to push the?vebranes together.The scale of this energy L0～O(n1)is consistent with the fact that the separation of the strands scales as√
-1
1
01
X
5
X 1
-10X 2
Figure 3:In the actual orbifold,the string source becomes N strings arrayed in a Z N symmetric fashion on a circle;here n 5=50,and N =5.The individual strings have been depicted with di?erent colors and thicknesses for ease of visualization.Remarks:
1.)It is important to note that,in the present context,U-duality and orbifolding do not commute.In the original F1-NS5background,the e?ect of the orbifold is to transform the background from the SL (2)invariant ground state of the spacetime CFT to a particular excited state
(σ??N )n 1n 5/N |0 (19)
on the BPS line L 0+c 8
We use the notation of the BPS states arising in the symmetric orbifold theory (T 4)n 1n 5/S n 1n 5,as twist ground states under the symmetric group.More generally,we can characterize the BPS states by the conjugacy class in the symmetric group S n 1n 5that they correspond to,and this sets
up an unambiguous relation between the symmetric orbifold twist states and the BPS states of the F1-NS5background with vanishing RR ?elds,the latter arising at a rather di?erent point in the moduli space of the spacetime CFT [48].
geometry,and not a transformed oscillator state in?at space,as is suggested by the above analysis.
2.)A related issue is the suggestion in[19],that there are new,nonperturbative kinds of orbifold constructions for N|n1n5but N|n5.There are U-duality transfor-mations that take n1,n5to n′1,n′5while keeping n1n5=n′1n′5,and such that N|n′5 but N|n5[48];the fact that there is a string theory orbifold in one U-duality frame but not the other suggested that there might be new kinds of orbifolds,hitherto unknown.We now understand that there is a BPS state(19)having the appropri-ate geometry(AdS3×S3)/Z N,but it will not have any kind of standard orbifold construction,in the sense of having twisted sectors of the usual type,etc.
3.)Nevertheless,all P-F1sources of the form(2)U-dualize(after smearing)into BPS geometries in the F1-NS5frame that seem to be exact worldsheet CFT’s.This is because all such geometries are1/4BPS,preserving eight supersymmetries.This amount of supersymmetry in spacetime is equivalent to N=(4,4)supersymmetry on the worldsheet;sigma models with this much supersymmetry are exact.In an orbifold CFT,the twisted sectors are an essential ingredient describing string theory on the geometry(13),in particular they resolve the singularity(provided there are no strong coupling singularities such as coincident?vebranes).Presumably there are states similarly localized near the singularity of the more general class of geometries associated to(2),for instance in the conical geometries of the previous remark;it would be very interesting to understand them,for instance their asymptotic density as discussed in[49],and their role in resolving the singularity in the geometry.
4.)The state that results from the orbifold operation is distinct from the corre-sponding BPS state of the N=4Liouville theory associated to AdS Chern-Simons supergravity,which is also associated to conical defects.As discussed for exam-ple in[50],the Liouville?eld is built(nonlocally)from the current sector of the spacetime CFT,and its Hilbert space has BPS states with the same quantum num-bers as(19);however,these states are distinct.In particular,there is no way to distinguish di?erent BPS states with the same quantum numbers J30,L0via their properties under the N=4currents.We will elaborate upon the role of the Liouville ?eld below.
To summarize,the orbifold operation in perturbative string theory maps global AdS3×S3to the geometry(13)of(AdS3×S3)/Z N.We can then consider the image of this map under the duality between bulk and boundary theories under the AdS/CFT correspondence.The global geometry AdS3×S3maps to the SL(2) invariant vacuum state of the dual CFT;correspondingly,the orbifold geometry (AdS3×S3)/Z N maps to the BPS state(19).
This correspondence has a fascinating re?ection in the orbifold(spacetime)CFT
(T4)n1n5/S n
1n5,which appears at a di?erent point in theΓ(n1n5)\O(5,4)/O(5)×
O(4)moduli space of the spacetime theory.9Twist?eld correlation functions of
a free?eld orbifold CFT may be computed by a general procedure that employs branched coverings of the Riemann surface on which the CFT vertex operators are inserted[51,52,53].The rami?cation points of the cover are the locations of the twist operator insertions.More recently,Lunin and Mathur[54,55]have adapted this method to compute the correlation functions of the twist operators of
the symmetric orbifold(T4)n1n5/S n
1n5.In this case,the rami?cation has the direct
interpretation of sewing together the di?erent copies of T4in the spacetime CFT, and there are remarkable simpli?cations in the structure of the correlation functions when one works on the covering space.For the particular case of the twist ground state(19),the two-point function corresponding to the propagation of this state is computed by passing to an N-fold branched cover,w=z1/N,of the CFT parameter space.Apart from the transformation of the measure(and a universal factor that implements the correct R-charge of the twist in the case of superconformal?eld theory),the covering space Riemann surface is the smooth two-sphere,and one is instructed to compute the vacuum partition function on the cover.The central charge?c of the covering space CFT is1/N of that of the original spacetime CFT, c=N?c,because of the N copies of T4CFT that have been sewn together in making the cover.10
But this structure is exactly that of the perturbative string theory orbifold (AdS3×S3)/Z N–namely,there is an N-fold covering space which is smooth,i.e.the global AdS3×S3vacuum spacetime(see?gure4).For example,the relation c=N?c of the central charges was noted in[50].It is standard to identify the parameter space of the CFT with the conformal boundary of AdS;the Euclidean continuation of AdS3to H+3=SL(2,C)/SU(2)has conformal boundary S2,and the orbifold operation of the bulk theory on H+3directly generates the branched cover seen in the representations of the twist correlators of the boundary theory.Once again we see a rather precise correspondence between bulk and boundary theories.Of course,the perturbative bulk orbifold and the symmetric orbifold boundary theory are at di?erent points in the moduli space of onebrane-?vebrane backgrounds,so one cannot compare directly;however,this remarkable parallel suggests to us that this property of covering onto smooth global AdS may be protected by supersymmetry as one travels across the moduli space.
Although it would appear that the perturbative string orbifold procedure can be directly mapped to a corresponding representation in the exact boundary CFT dual,perhaps a note of caution is in order–the precise correspondence may be special to BPS states.In[50],a set of nonsupersymmetric orbifolds(AdS3/Z N)×S3was also considered.In this case,N can be arbitrarily large(in particular it need not divide n1n5).The perturbative spectrum of such orbifolds is tachyonic, indicating[50,56]that they decay via the emission of a pulse of string excitations,
-101
-101
-1
1
Figure 4:The (AdS 3×S 3)/Z N orbifold geometry covers smoothly onto global AdS 3×S 3.Here we have indicated the slicing of the global space into fundamental domains,with the quotient space being the conically singular geometry.This same covering procedure is involved in computations of twist operators in the (T 4)n 1n 5/S n 1n 5orbifold related to the dual spacetime CFT.
eventually settling down to an ordinary excited state of AdS 3×S 3with the same quantum numbers.This state cannot have a naive covering space interpretation of the type considered above –the covering CFT would have central charge ?c =6n 1n 5/N ,and N can be arbitrarily large.Of course,the e?ect on the central charge is a special construction for twist operators of the symmetric group.There is certainly a covering interpretation for general Z N twists in terms of a CFT of the same central charge as the original theory [51,52,53],but the path integral on the covering space is constrained –the ?elds must take on Z N related values at Z N related points on the covering space.It is only in the case of the symmetric orbifold twist operators that the covering space path integral is an unconstrained path integral [54,55]in terms of a theory with central charge N times smaller (i.e.n 1n 5/N copies of the component CFT underlying the symmetric product).There might be a description of the (AdS 3/Z N )×S 3orbifold in terms of a twist operator in the dual CFT,of this more general type.
This description of BPS states and correlators in the spacetime CFT also sheds light on the role of the Liouville ?eld that summarizes Chern-Simons AdS 3super-gravity [57].The covering transformation yields a smooth Riemann surface from one with Z N conical defects,but the corresponding coordinate map w =z 1/N a?ects the path integral via the conformal anomaly.As discussed for instance in [50],the Liouville ?eld ?L =log |?z/?w |2summarizes the physical data of the Chern-Simons supergravity connection,in this instance the coordinate map relating ?at space and
the conical defect.Correspondingly,in[54,55]this same Liouville?eld arises in the covering onto the vacuum spacetime via the conformal anomaly,and for the same reason–the gauge invariant modes of Chern-Simons supergravity can be identi?ed with the modes of the current sector of the spacetime CFT.
3The excitation spectrum
Having identi?ed the state in the exact spacetime CFT corresponding to the per-turbative(AdS3×S3)/Z N orbifold,we can now give a direct interpretation of the spectrum of low-energy perturbative string excitations around the orbifold.These consist of
?Untwisted short string states.These are characterized by their representation labels(j,m,ˉm;j′,m′,ˉm′)under the worldsheet left and right SL(2,R)×SU(2) current algebra,together with the oscillator content.The SL(2)spin j lies in the principal discrete series,j∈R,1
n5+
j′(j′+1)
2
,(20)
so the integer gap in oscillator number results in a gap in spacetime energy ?L0of orderδj～√
n5/N.In particular,for N～n5,the gap becomes of the same order as that of the supergravity modes–there is no regime where supergravity is an e?ective approximation to the dynamics!
?Long string states.These states arise from principal continuous series repre-sentations[58]with j=1
4+
1
4n5
+h int?1
separating ?vebranes from the background ensemble.In the orbifold theory,fractional spectral ?ow by w =p/N is allowed,provided one ?ows by an amount ?p/N in SU (2);this means that the internal level is
h int =j ′(j ′+1)
4w 2+N osc .(22)
Setting m ′=0for simplicity,one sees that (after exciting a fermion oscillator N osc =1
N p +N
4n 5+
j ′(j ′+1)
N ?L 0.(24)
In particular,the gap in supergravity excitations is the inverse AdS radius ??1in global AdS ,and (N?)?1in the orbifold theory.In global AdS ,the gap in the spacetime energy m +ˉm and angular momentum m ?ˉm of the AdS modes of a given supergravity ?eld (?xing also the quantum numbers on S 3)is accounted for by the fact that the modes are spanned by the action of L ?1,ˉL ?1on the highest weight state:
ΦSL (2)j m ˉm =(L ?1)m (ˉL ?1)ˉm ΦSL (2)j 00.
(25)Thus the gap in energy is 1/?(recall that spacetime energy is ?E =L 0+ˉL 0).In the orbifold spacetime,L ?1descends from ?L ?N on the covering space,and does not span the full set of modes;thus,the ΦSL
(2)j m ˉm are not related by the spacetime
superconformal algebra.Shifting m +ˉm by two (keeping m ?ˉm ?xed)results in a change of the energy by an amount 2/N?.
This energy gap is inversely related to the return time of supergravity probes sent radially inward from the top of the throat in the full asymptotically ?at D1-D5geometry,?t =π√a ,(26)
as noted in[11];for the orbifold backgrounds,one has?t=Nπ.Our point here
is that this time scale remains visible in the near-horizon limit,as the gap in the
spectrum relative to the AdS scale.The e?ect of the orbifold is indeed to make a deeper gravitational well in the center of AdS,as expected from the fact that the
conical defect starts to approach the black hole limit from below at large N.The closer one approaches the black hole threshold,the smaller the gap in the spectrum,
due to the increasing redshift generated by the large mass at the center of AdS.At
the extremal black hole point L0=c/12=T30,the spectrum becomes continuous (in the classical theory).
We may interpret these various excitations in terms of the underlying brane
dynamics as follows.The untwisted string states are related to the singlet sector –the overall U(1)of the U(N)gauge dynamics–of the?vebrane dual.This is in
accord with the standard AdS/CFT duality between gauge invariant local operators and supergravity modes.The twisted sectors are the‘Cartan’multiplets describing
individual groups of n5/N?vebranes(so one has the full set of Cartan modes for
N=n5),since the twisted sector moduli describe relative overall motion of the branes.The o?-diagonal modes of?vebrane gauge dynamics are described as the
fractional D-strings of the orbifold.Indeed,the separation of strands in the dual string source of global AdS of?gure1, n1/n5.In the orbifold theory,the separation of the strands of the dual string decreases by a factor
of N,reducing the energy cost of fractional D-strings in the F1-NS5frame by a
corresponding factor.Note that there are no noncompact spatial directions into which the RR?ux of these fractional branes may escape;thus the fractional branes must always organize themselves into regular representation branes carrying no net fractional D1charge;such branes can then disappear by leaving the?vebranes and decaying into untwisted string modes.This is a re?ection of Gauss’law in the ?vebrane gauge theory.
One should also note that the twisted moduli of the orbifold are e?ectively1+1
dimensional scalar?elds,and so it is somewhat misleading to consider them as having expectation values as we have been doing.This is an artifact of the tree level approximation to the orbifold dynamics in perturbative string theory.At one loop,one will encounter an infrared divergence arising from the?uctuations of the moduli,and one will have to quantize them as collective coordinates(c.f.[59]).The moduli are thus the coordinates of a wavefunction for the?vebrane sources,whose understanding will require knowledge of the dynamics near the singular regions where?vebranes coincide.
It was noted in[19]that the gap to black hole states above the(AdS3×S3)/Z N orbifold is of order n1n5/N2,which is of order n1/n5=g26when N=n511.There are two interesting interpretations of this scale.First,the energy to remove a fundamen-tal string from the background ensemble is of order n5;thus,the black hole threshold
is of order the energy required to remove all the strings from the background and put them on their Coulomb branch.Left behind would be a strong-coupling throat of the n 5?vebranes,indicating the appearance of strong-coupling dynamics.Sec-ond,the energy cost of D-branes is of order 1/g 6=
n 1/n 5D-branes,so that the e?ective gauge coupling
g 6n D
～1,and again the dynamics is strongly coupled.We regard these two es-timates as yet another indication that the onset of black hole physics is a strong coupling phenomenon from the point of view of string dynamics.
4An aside on ?vebranes
The smearing of sources to obtain the geometry seen by low-energy string theory has applications to other backgrounds,in particular that of NS5-branes on the Coulomb branch studied in [47,60].There,it was claimed that the nonsingular coset CFT
(SL (2,C )U (1))/Z n 513
describes the four-dimensional transverse space of separated ?vebranes.On the other hand,supergravity would suggest that the target space
is that of the multicenter CHS throat solution (directions along the ?vebranes are suppressed)
ds 2=?dt 2+H 5 |dz |2+|dw |2
e 2Φ=H 5(27)
dB =?d ΦH 5=n 5
α=1
1
sinh 2ρ+cos 2θdψ2+cosh 2
ρsin 2θ
U (1)×U (1),describing charged black holes,was considered
in [61].After a Wick rotation to Euclidean AdS 3,and taking the limit of the charge parameter Q 2→?1(in the conventions of [61]),one ?nds that the extra U (1)
decouples and the geometry becomes precisely that of(28)!Thus,smearing of the source provides the connection between the CHS geometry and the exact sigma model description of[47].Note that smearing does not remove the singularities in the metric and dilaton;these still appear in(28),however they are apparently harmless in string theory,since the correlation functions of the coset are entirely well-behaved(at least at su?ciently low energy[47,60]).This is a re?ection of the absence of throat dynamics for separated?vebranes.Once again,the string theory remembers that the sources are localized and not smeared;for instance,D-strings stretch between speci?c Z N symmetric points along the locus sinh2ρ+cos2θ= 0[62,63].
5Comments on BTZ orbifolds,and cosmology
In this section we try to apply some of the lessons learned above in the study of rotational orbifolds of AdS3×S3to other contexts,speci?cally the class of orbifolds that realize BTZ black holes as quotients of AdS3[20,21].
5.1The BTZ geometry as an AdS3quotient
Group elements h∈SL(2,R)lie in one of three conjugacy classes–elliptic,parabolic, and hyperbolic,depending on whether|Tr[h]|is less than,equal to,or greater than two,respectively(the trace is in the two-dimensional representation).Elliptic ele-ments are conjugate to a rotation,and lead to the class of conical defect spacetimes discussed above.The orbifold
g～hgh,g∈SL(2,R)(29) of AdS3by the action of the discrete group generated by a hyperbolic element h, leads to a fundamental domain of the identi?cation which contains the BTZ black hole spacetime with zero angular momentum(J=0)[20,21](the identi?cation by a parabolic element yields the extremal(?M=J)BTZ black hole).Let us parametrize g∈SL(2,R)via the analogue of Euler angles
g=e(t?φ)iσ2/2eρσ3e(t+φ)iσ2/2≡ a b c d (30)
; = cos(t)cosh(ρ)+cos(φ)sinh(ρ)sin(t)cosh(ρ)+sin(φ)sinh(ρ)?sin(t)cosh(ρ)+sin(φ)sinh(ρ)cos(t)cosh(ρ)?cos(φ)sinh(ρ)
in these coordinates,the metric on AdS3takes the form
=?2 ?cosh2ρdt2+dρ2+sinh2ρdφ2 .(31) ds2
AdS
The BTZ black hole geometry results from the identi?cation(29),with h= exp[πr+σ3];the mass of the BTZ black hole will then be?M=1
Spring Security-3.0.1 中文官方文档（翻译版） 这次发布的Spring Security-3.0.1 是一个bug fix 版，主要是对3.0 中存在的一些问题进行修 正。文档中没有添加新功能的介绍，但是将之前拼写错误的一些类名进行了修正，建议开发者以这一版本的文档为参考。 另：Spring Security 从2010-01-01 以后，版本控制从SVN 换成了GIT，我们在翻译文档的时候，主要是根据SVN 的变化来进行文档内容的比对，这次换成GIT 后，感觉缺少了之前那种文本比对工具，如果有对GIT 熟悉的朋友，还请推荐一下文本比对的工具，谢谢。 序言 I. 入门 1. 介绍 1.1. Spring Security 是什么？ 1.2. 历史 1.3. 发行版本号 1.4. 获得Spring Security 1.4.1. 项目模块 1.4.1.1. Core - spring-security-core.jar 1.4.1. 2. Web - spring-security-web.jar 1.4.1.3. Config - spring-security-config.jar 1.4.1.4. LDAP - spring-security-ldap.jar 1.4.1.5. ACL - spring-security-acl.jar 1.4.1.6. CAS - spring-security-cas-client.jar 1.4.1.7. OpenID - spring-security-openid.jar 1.4. 2. 获得源代码 2. Security 命名空间配置 2.1. 介绍 2.1.1. 命名空间的设计 2.2. 开始使用安全命名空间配置 2.2.1. 配置web.xml 2.2.2. 最小
2．1、Spring Web MVC是什么 Spring Web MVC是一种基于Java的实现了Web MVC设计模式的请求驱动类型的轻量级Web框架，即使用了MVC架构模式的思想，将web层进行职责解耦，基于请求驱动指的就是使用请求-响应模型，框架的目的就是帮助我们简化开发，Spring Web MVC也是要简化我们日常Web开发的。 另外还有一种基于组件的、事件驱动的Web框架在此就不介绍了，如Tapestry、JSF等。 Spring Web MVC也是服务到工作者模式的实现，但进行可优化。前端控制器是DispatcherServlet；应用控制器其实拆为处理器映射器(Handler Mapping)进行处理器管理和视图解析器(View Resolver)进行视图管理；页面控制器/动作/处理器为Controller接口（仅包含ModelAndView handleRequest(request, response) 方法）的实现（也可以是任何的POJO类）；支持本地化（Locale）解析、主题（Theme）解析及文件上传等；提供了非常灵活的数据验证、格式化和数据绑定机制；提供了强大的约定大于配置（惯例优先原则）的契约式编程支持。 2．2、Spring Web MVC能帮我们做什么 √让我们能非常简单的设计出干净的Web层和薄薄的Web层； √进行更简洁的Web层的开发；
√天生与Spring框架集成（如IoC容器、AOP等）； √提供强大的约定大于配置的契约式编程支持； √能简单的进行Web层的单元测试； √支持灵活的URL到页面控制器的映射； √非常容易与其他视图技术集成，如Velocity、FreeMarker等等，因为模型数据不放在特定的API里，而是放在一个Model里（Map数据结构实现，因此很容易被其他框架使用）； √非常灵活的数据验证、格式化和数据绑定机制，能使用任何对象进行数据绑定，不必实现特定框架的API； √提供一套强大的JSP标签库，简化JSP开发； √支持灵活的本地化、主题等解析； √更加简单的异常处理； √对静态资源的支持； √支持Restful风格。 2．3、Spring Web MVC架构
java基础教程:Java基础 疯狂代码 https://www.doczj.com/doc/242571725.html,/ ?:http:/https://www.doczj.com/doc/242571725.html,/BlogDigest/Article75483.html Java简介 Java是由Sun Microsystems公司于1995年5月推出的Java程序设计语言（以下简称Java语言）和Java平台的总称。用Java实现的HotJava浏览器（支持Java applet）显示了Java的魅力：跨平台、动态的Web、Internet计算。从此，Java被广泛接受并推动了Web的迅速发展，常用的浏览器现在均支持Java applet。另一方面，Java技术也不断更新。 Java平台由Java虚拟机（Java Virtual Machine）和Java 应用编程接口（Application Programming Interface、简称API）构成。Java 应用编程接口为Java应用提供了一个独立于操作系统的标准接口，可分为基本部分和扩展部分。在硬件或操作系统平台上安装一个Java平台之后，Java应用程序就可运行。现在Java平台已经嵌入了几乎所有的操作系统。这样Java程序可以只编译一次，就可以在各种系统中运行。Java应用编程接口已经从1.1x版发展到1.2版。目前常用的Java平台基于Java1.4，最近版本为Java1.7。 Java分为三个体系JavaSE(Java2 Platform Standard Edition，java平台标准版 )，JavaEE(Java 2 Platform,Enterprise Edition，java平台企业版)，JavaME(Java 2 Platform Micro Edition，java平台微型版)。 2009年04月20日，oracle（甲骨文)宣布收购sun。 1991年，Sun公司的James Gosling。Bill Joe等人，为电视、控制考面包机等家用电器的交互操作开发了一个Oak（一种橡树的名字）软件，他是Java的前身。当时，Oak并没有引起人们的注意，直到1994年，随着互联网和3W的飞速发展，他们用Java编制了HotJava浏览器，得到了Sun公司首席执行官Scott McNealy的支持，得以研发和发展。为了促销和法律的原因，1995年Oak更名为Java。Java的得名还有段小插曲呢，一天，Java小组成员正在喝咖啡时，议论给新语言起个什么名字的问题，有人提议用Java（Java是印度尼西亚盛产咖啡的一个岛屿），这个提议得到了其他成员的赞同，于是就采用Java来命名此新语言。很快Java被工业界认可，许多大公司如IBM Microsoft.DEC等购买了Java的使用权，并被美国杂志PC Magazine评为1995年十大优秀科技产品。从此，开始了Java应用的新篇章。 Java的诞生时对传统计算机模式的挑战，对计算机软件开发和软件产业都产生了深远的影响： （1）软件4A目标要求软件能达到任何人在任何地方在任何时间对任何电子设备都能应用。这样能满足软件平台上互相操作，具有可伸缩性和重要性并可即插即用等分布式计算模式的需求。 （2）基于构建开发方法的崛起，引出了CORBA国际标准软件体系结构和多层应用体系框架。在此基础上形成了Java.2平台和.NET平台两大派系，推动了整个IT业的发展。 （3）对软件产业和工业企业都产生了深远的影响，软件从以开发为中心转到了以服务为中心。中间提供商，构件提供商，服务器软件以及咨询服务商出现。企业必须重塑自我，B2B的电子商务将带动整个新经济市场，使企业获得新的价值，新的增长，新的商机，新的管理。 （4）对软件开发带来了新的革命，重视使用第三方构件集成，利用平台的基础设施服务，实现开发各个阶段的重要技术，重视开发团队的组织和文化理念，协作，创作，责任，诚信是人才的基本素质。 总之，目前以看到了Java对信息时代的重要性，未来还会不断发展，Java在应用方面将会有更广阔的前景。 ; JAVA-名字起源 Java自1995诞生，至今已经14年历史。Java的名字的来源：Java是印度尼西亚爪哇岛的英文名称，因盛产咖啡而闻名。Java语言中的许多库类名称，多与咖啡有关，如JavaBeans(咖啡豆)、NetBeans(网络豆)以及ObjectBeans (对象豆)等等。SUN和JAVA的标识也正是一杯正冒着热气的咖啡。 据James Gosling回忆，最初这个为TV机顶盒所设计的语言在Sun内部一直称为Green项目。我们的新语言需要一个名字。Gosling注意到自己办公室外一棵茂密的橡树Oak，这是一种在硅谷很常见的树。所以他将这个新语言命名为Oak。但Oak是另外一个注册公司的名字。这个名字不可能再用了。 在命名征集会上，大家提出了很多名字。最后按大家的评选次序，将十几个名字排列成表，上报给商标律师。排在第一位的是Silk(丝绸
spring mvc学习教程(一)-入门实例 引言 1.MVC：Model-View-Control 框架性质的C层要完成的主要工作：封装web请求为一个数据对象、调用业务逻辑层来处理数据对象、返回处理数据结果及相应的视图给用户。 2.简要概述springmvc Spring C 层框架的核心是DispatcherServlet，它的作用是将请求分发给不同的后端处理器，也即使用了一种被称为Front Controller 的模式（后面对此模式有简要说明）。Spring 的C 层框架使用了后端控制器来、映射处理器和视图解析器来共同完成C 层框架的主要工作。并且spring 的C 层框架还真正地把业务层处理的数据结果和相应的视图拼成一个对象，即我们后面会经常用到的ModelAndView 对象。 一、入门实例 1. 搭建环境 在spring的官方API文档中，给出所有包的作用概述，现列举常用的包及相关作用： org.springframework.aop-3.0.5.RELEASE.jar：与Aop编程相关的包 org.springframework.beans-3.0.5.RELEASE.jar：提供了简捷操作bean的接口org.springframework.context-3.0.5.RELEASE.jar：构建在beans包基础上，用来处理资源文件及国际化。 org.springframework.core-3.0.5.RELEASE.jar：spring核心包 org.springframework.web-3.0.5.RELEASE.jar：web核心包，提供了web层接口org.springframework.web.servlet-3.0.5.RELEASE.jar：web 层的一个具体实包，DispatcherServlet也位于此包中。 后文全部在spring3.0 版本中进行，为了方便，建议在搭建环境中导入spring3.0 的所有jar 包（所有jar 包位于dist 目录下）。 2.编写HelloWorld实例 步骤一、建立名为springMVC_01_helloword，并导入上面列出的jar 包。 步骤二、编写web.xml配置文件，代码如下：
Spring开发教程 Spring教程 (1) Spring框架概述 (2) Spring是什么？ (2) Spring的历史 (3) Spring的使命（Mission Statement） (3) Spring受到的批判 (3) Spring包含的模块 (4) 总结 (5) Spring的IoC容器 (6) 用户注册的例子 (6) 面向接口编程 (7) （用户持久化类）重构第一步——面向接口编程 (8) 重构第二步——工厂（Factory）模式 (9) 重构第三步——工厂（Factory）模式的改进 (9) 重构第四步－IoC容器 (10) 控制反转（IoC）/依赖注入（DI） (10) 什么是控制反转/依赖注入？ (10) 依赖注入的三种实现形式 (11) BeanFactory (13) BeanFactory管理Bean（组件）的生命周期 (14) Bean的定义 (15) Bean的之前初始化 (19) Bean的准备就绪（Ready）状态 (21) Bean的销毁 (21) ApplicationContext (21) Spring的AOP框架 (21) Spring的数据层访问 (21) Spring的声明式事务 (21) Spring对其它企业应用支持 (22)
名词解释 容器： 框架： 框架 容器 组件： 服务： Spring框架概述 主要内容：介绍Spring的历史，Spring的概论和它的体系结构，重点阐述它在J2EE中扮演的角色。 目的：让学员全面的了解Spring框架，知道Spring框架所提供的功能，并能将Spring 框架和其它框架（WebWork/Struts、hibernate）区分开来。 Spring是什么？ Spring是一个开源框架，它由Rod Johnson创建。它是为了解决企业应用开发的复杂性而创建的。Spring使用基本的JavaBean来完成以前只可能由EJB完成的事情。然而，Spring 的用途不仅限于服务器端的开发。从简单性、可测试性和松耦合的角度而言，任何Java应用都可以从Spring中受益。 ?目的：解决企业应用开发的复杂性 ?功能：使用基本的JavaBean代替EJB，并提供了更多的企业应用功能 ?范围：任何Java应用 简单来说，Spring是一个轻量级的控制反转(IoC)和面向切面(AOP)的容器框架。 ■轻量——从大小与开销两方面而言Spring都是轻量的。完整的Spring框架可以在一个大小只有1MB多的JAR文件里发布。并且Spring所需的处理开销也是微不足道的。此外，Spring是非侵入式的：典型地，Spring应用中的对象不依赖于Spring的特定类。 ■控制反转——Spring通过一种称作控制反转（IoC）的技术促进了松耦合。当应用了IoC，一个对象依赖的其它对象会通过被动的方式传递进来，而不是这个对象自己创建或者查找依赖对象。你可以认为IoC与JNDI相反——不是对象从容器中查找依赖，而是容器在对象初始化时不等对象请求就主动将依赖传递给它。 ■面向切面——Spring提供了面向切面编程的丰富支持，允许通过分离应用的业务逻辑与系统级服务（例如审计（auditing）和事务（）管理）进行内聚性的开发。应用对象只实
Spring基础入门 一、基础知识 1.依赖注入、控制反转 依赖注入：在运行期，由外部容器动态地将依赖对象注入到组件中 控制反转：应用本身不负责依赖对象的创建及维护，依赖对象的创建及维护是由外部窗口负责得。这样控制权就由应用转移到了外部容器，控制权的转移就是所谓的反转。 2.spring 的主要特性。 （1）降低组件之间的耦合度，实现软件各层之间的解耦。 （2）可以使用容器提供的众多服务，如：事务管理服务、消息服务、JMS 服务、持久化服务等等。 （3）容器提供单例模式支持，开发人员不再需要自己编写实现代码。 （4）容器提供了AOP 技术，利用它很容易实现如权限拦截，运行期监控等功能。 （5）容器提供的众多辅作类，使用这些类能够加快应用的开发，如：JdbcTemplate、HibernateTemplate. （6）对主流的应用框架提供了集成支持。 3.常用技术 控制反转/依赖注入---面向切入编程---与主流框架的整合、管理--- 二、实例拓展 1.准备搭建环境 dist\spring.jar lib\jakata-commons\commons-loggin.jar 如果使用了切面编程，还需下列jar 文件： lib\aspectj\aspectjweaver.jar 和aspectjrt.jar lib\cglib\cglib-nodep-2.1.3.jar 如果使用了jsr-250 中的注解，还需要下列jar 文件： lib\j2ee\common-annotations.jar 2.搭建并测试环境 建立名为spring_01_base项目，根据需求导入jar包。建立一个Junit测试单元SpringEnvTest，测试代码如下： @Test public void testEnv() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); } beans.xml 配置文件在此省略（见下）。运行此测试如无错，则说明环境搭建成功。 说明：beans.xml 可以在类路径下进行配置，也可以在具体的目录下配置。可以是一个配置文件，也可以是多个配置文件组成String 数组传入。 3.实例 作如下准备工作：（1）建立UseDao接口，代码如下： package com.asm.dao; public interface UserDao { void save(); }
Spring教程 作者：钱安川（Moxie）
Spring教程 (1) Spring框架概述 (3) Spring是什么？ (3) Spring的历史 (4) Spring的使命（Mission Statement） (4) Spring受到的批判 (4) Spring包含的模块 (5) 总结 (6) Spring的IoC容器 (6) 用户注册的例子 (7) 面向接口编程 (8) （用户持久化类）重构第一步——面向接口编程 (8) 重构第二步——工厂（Factory）模式 (9) 重构第三步——工厂（Factory）模式的改进 (10) 重构第四步－IoC容器 (11) 控制反转（IoC）/依赖注入（DI） (11) 什么是控制反转/依赖注入？ (11) 依赖注入的三种实现形式 (12) BeanFactory (14) BeanFactory管理Bean（组件）的生命周期 (15) Bean的定义 (16) Bean的之前初始化 (19) Bean的准备就绪（Ready）状态 (21) Bean的销毁 (21) ApplicationContext (21) Spring的AOP框架 (21) Spring的数据层访问..................................................................................... 错误！未定义书签。Spring的声明式事务..................................................................................... 错误！未定义书签。Spring对其它企业应用支持......................................................................... 错误！未定义书签。 名词解释 容器： 框架： 组件： 服务：
Spring教程
Spring教程 (1) Spring框架概述 (3) Spring是什么？ (3) Spring的历史 (4) Spring的使命（Mission Statement） (4) Spring受到的批判 (4) Spring包含的模块 (4) 总结 (6) Spring的IoC容器 (6) 用户注册的例子 (7) 面向接口编程 (8) （用户持久化类）重构第一步——面向接口编程 (8) 重构第二步——工厂（Factory）模式 (9) 重构第三步——工厂（Factory）模式的改进 (10) 重构第四步－IoC容器 (10) 控制反转（IoC）/依赖注入（DI） (11) 什么是控制反转/依赖注入？ (11) 依赖注入的三种实现形式 (12) BeanFactory (14) BeanFactory管理Bean（组件）的生命周期 (14) Bean的定义 (15) Bean的之前初始化 (18) Bean的准备就绪（Ready）状态 (21) Bean的销毁 (21) ApplicationContext (21) Spring的AOP框架 (21) Spring的数据层访问 (21) Spring的声明式事务 (21) Spring对其它企业应用支持 (21) 名词解释 容器： 框架： 组件： 服务：
Spring框架概述 主要内容：介绍Spring的历史，Spring的概论和它的体系结构，重点阐述它在J2EE中扮演的角色。 目的：让学员全面的了解Spring框架，知道Spring框架所提供的功能，并能将Spring 框架和其它框架（WebWork/Struts、hibernate）区分开来。 Spring是什么？ Spring是一个开源框架，它由Rod Johnson创建。它是为了解决企业应用开发的复杂性而创建的。Spring使用基本的JavaBean来完成以前只可能由EJB完成的事情。然而，Spring 的用途不仅限于服务器端的开发。从简单性、可测试性和松耦合的角度而言，任何Java应用都可以从Spring中受益。 ?目的：解决企业应用开发的复杂性 ?功能：使用基本的JavaBean代替EJB，并提供了更多的企业应用功能 ?范围：任何Java应用 简单来说，Spring是一个轻量级的控制反转(IoC)和面向切面(AOP)的容器框架。 ■轻量——从大小与开销两方面而言Spring都是轻量的。完整的Spring框架可以在一个大小只有1MB多的JAR文件里发布。并且Spring所需的处理开销也是微不足道的。此外，Spring是非侵入式的：典型地，Spring应用中的对象不依赖于Spring的特定类。 ■控制反转——Spring通过一种称作控制反转（IoC）的技术促进了松耦合。当应用了IoC，一个对象依赖的其它对象会通过被动的方式传递进来，而不是这个对象自己创建或者查找依赖对象。你可以认为IoC与JNDI相反——不是对象从容器中查找依赖，而是容器在对象初始化时不等对象请求就主动将依赖传递给它。 ■面向切面——Spring提供了面向切面编程的丰富支持，允许通过分离应用的业务逻辑与系统级服务（例如审计（auditing）和事务（）管理）进行内聚性的开发。应用对象只实现它们应该做的——完成业务逻辑——仅此而已。它们并不负责（甚至是意识）其它的系统级关注点，例如日志或事务支持。 ■容器——Spring包含并管理应用对象的配置和生命周期，在这个意义上它是一种容器，你可以配置你的每个bean如何被创建——基于一个可配置原型（prototype），你的bean 可以创建一个单独的实例或者每次需要时都生成一个新的实例——以及它们是如何相互关联的。然而，Spring不应该被混同于传统的重量级的EJB容器，它们经常是庞大与笨重的，难以使用。 ■框架——Spring可以将简单的组件配置、组合成为复杂的应用。在Spring中，应用对象被声明式地组合，典型地是在一个XML文件里。Spring也提供了很多基础功能（事务管理、持久化框架集成等等），将应用逻辑的开发留给了你。 所有Spring的这些特征使你能够编写更干净、更可管理、并且更易于测试的代码。它
Spring3 MVC - 3到Spring MVC框架简介 Spring3 MVC框架简介 Spring MVC是Spring的框架的Web组件。它提供了丰富的功能，为建设强大的Web应用程序。Spring MVC框架的架构，并在这样的高度可配置的方式，每一块的逻辑和功能设计。此外Spring可以毫不费力地与其他流行的Web框架，如Struts，WebWork的，的Java Server Faces和Tapestry集成。这意味着，你甚至可以告诉Spring使用Web框架中的任何一个。比Spring更不紧耦合的servlet或JSP 向客户端呈现视图。喜欢速度与其他视图技术集成，Freemarker的，Excel或PDF现在也有可能。 Spring3.0 MVC系列 ?第1部分：到Spring 3.0 MVC框架简介 ?第2部分：在Spring 3.0 MVC创建Hello World应用程序 ?第3部分：在Spring 3.0 MVC的形式处理 ?第4部分：Spring3 MVC的Tiles Support与Eclipse中的例子插件教程 ?第5部分：Spring3 MVC的国际化及本地化教程与范例在Eclipse ?第6部分：Spring3 MVC示例教程Spring主题 ?第7部分：创建Spring3 MVC Hibernate 3的示例在Eclipse中使用Maven的 在Spring Web MVC，你可以使用任何对象作为命令或表单支持对象，你不需要实现框架特定的接口或基类。Spring的数据绑定是高度灵活的：例如，将验证错误类型不作为应用系统错误，可以通过评估的不匹配。因此，你不必重复你的业务对象的属性，简单的无类型的字符串，在表单对象仅仅是为了处理无效的意见，或正确转换的字符串。相反，它往往是最好直接绑定到业务对象。 请求处理生命周期 Spring的Web MVC框架是，像许多其他Web MVC框架，要求为导向，围绕一个中心的servlet，它把请求分派给控制器，提供其他功能，有利于开发Web应用而设计的。Spring DispatcherServlet DispatcherServlet是Spring IoC容器完全集成，并允许我们使用的每一个Spring的其他功能。
一、理论知识 1.依赖注入、控制反转 依赖注入：在运行期，由外部容器动态地将依赖对象注入到组件中 控制反转：应用本身不负责依赖对象的创建及维护，依赖对象的创建及维护是由外部窗口负责得。这样控制权就由应用转移到了外部容器，控制权的转移就是所谓的反转。 2.spring 的主要特性。 （1）降低组件之间的耦合度，实现软件各层之间的解耦。 （2）可以使用容器提供的众多服务，如：事务管理服务、消息服务、JMS 服务、持久化服务等等。 （3）容器提供单例模式支持，开发人员不再需要自己编写实现代码。 （4）容器提供了AOP 技术，利用它很容易实现如权限拦截，运行期监控等功能。 （5）容器提供的众多辅作类，使用这些类能够加快应用的开发，如：JdbcTemplate、HibernateTemplate. （6）对主流的应用框架提供了集成支持。 3.常用技术 控制反转/依赖注入---面向切入编程---与主流框架的整合、管理--- 二、基本实例 1.准备搭建环境 dist\spring.jar lib\jakata-commons\commons-loggin.jar 如果使用了切面编程，还需下列jar 文件： lib\aspectj\aspectjweaver.jar 和aspectjrt.jar lib\cglib\cglib-nodep-2.1.3.jar 如果使用了jsr-250 中的注解，还需要下列jar 文件： lib\j2ee\common-annotations.jar 2.搭建并测试环境 建立名为spring_01_base项目，根据需求导入jar包。建立一个Junit测试单元SpringEnvTest，测试代码如下： @Test public void testEnv() { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); } beans.xml 配置文件在此省略（见下）。运行此测试如无错，则说明环境搭建成功。 说明：beans.xml 可以在类路径下进行配置，也可以在具体的目录下配置。可以是一个配置文件，也可以是多个配置文件组成String 数组传入。 3.实例 作如下准备工作：（1）建立UseDao接口，代码如下： package com.asm.dao; public interface UserDao { void save(); } （2）建立UserDao接口的实现类，UserDaoImpl package com.asm.dao.impl;
尚学堂马士兵Spring文档 课程内容 1.面向接口（抽象）编程的概念与好处 2.IOC/DI的概念与好处 a)inversion of control b)dependency injection 3.AOP的概念与好处 4.Spring简介 5.Spring应用IOC/DI（重要） a)xml b)annotation 6.Spring应用AOP（重要） a)xml b)annotation 7.Struts2.1.6 + Spring2.5.6 + Hibernate3.3.2整合（重要） a)opensessionInviewfilter（记住，解决什么问题，怎么解决） 8.Spring JDBC 面向接口编程（面向抽象编程） 1.场景：用户添加 2.Spring_0100_AbstractOrientedProgramming a)不是AOP:Aspect Oriented Programming 3.好处：灵活 什么是IOC（DI），有什么好处 1.把自己new的东西改为由容器提供 a)初始化具体值 b)装配 2.好处：灵活装配
Spring简介 1.项目名称：Spring_0200_IOC_Introduction 2.环境搭建 a)只用IOC i.spring.jar , jarkata-commons/commons-loggin.jar 3.IOC容器 a)实例化具体bean b)动态装配 4.AOP支持 a)安全检查 b)管理transaction Spring IOC配置与应用 1.FAQ:不给提示： a)window – preferences – myeclipse – xml – xml catalog b)User Specified Entries – add i.Location: D:\share\0900_Spring\soft\spring-framework-2.5.6\dist\resources\sprin g-beans-2.5.xsd ii.URI: file:///D:/share/0900_Spring/soft/spring-framework-2.5.6/dist/resource s/spring-beans-2.5.xsd iii.Key Type: Schema Location iv.Key: https://www.doczj.com/doc/242571725.html,/schema/beans/spring-beans-2.5.xsd 2.注入类型 a)Spring_0300_IOC_Injection_Type b)setter（重要） c)构造方法（可以忘记） d)接口注入（可以忘记） 3.id vs. name a)Spring_0400_IOC_Id_Name b)name可以用特殊字符 4.简单属性的注入 a)Spring_0500_IOC_SimpleProperty b) Spring入门教程 中国软件评测中心陈兵1．Spring简介 （1）Spring是什么 Spring是轻量级的J2EE应用程序开源框架。它由Rod Johnson创建。它是为了解决企业应用开发的复杂性而创建的。Spring使用基本的JavaBean来完成以前只可能由EJB完成的事情。然而，Spring的用途不仅限于服务器端的开发。从简单性、可测试性和松耦合的角度而言，任何Java应用都可以从Spring中受益。 Spring的核心是个轻量级容器（container），实现了IoC（Inversion of Control）模式的容器，Spring的目标是实现一个全方位的整合框架，在Spring 框架下实现多个子框架的组合，这些子框架之间彼此可以独立，也可以使用其它的框架方案加以替代，Spring希望提供one-stop shop的框架整合方案Spring不会特别去提出一些子框架来与现有的OpenSource框架竞争，除非它觉得所提出的框架够新够好，例如Spring有自己的 MVC框架方案，因为它觉得现有的MVC方案有很多可以改进的地方，但它不强迫您使用它提供的方案，您可以选用您所希望的框架来取代其子框架，例如您仍可以在Spring中整合您的Struts框架。 Spring的核心概念是IoC，IoC的抽象概念是「依赖关系的转移」，像是「高层模块不应该依赖低层模块，而是模块都必须依赖于抽象」是IoC的一种表现，「实现必须依赖抽象，而不是抽象依赖实现」也是IoC的一种表现，「应用程序不应依赖于容器，而是容器服务于应用程序」也是IoC的一种表现。回想一下面向对象的设计原则：OCP原则和DIP原则。 Spring的核心即是个IoC/DI的容器，它可以帮程序设计人员完成组件（类别们）之间的依赖关系注入（连结），使得组件（类别们）之间的依赖达到最小，进而提高组件的重用性，Spring是个低侵入性（invasive）的框架，Spring中的组件并不会意识到它正置身于Spring中，这使得组件可以轻易的从框架中脱离，而几乎不用任何的修改，反过来说，组件也可以简单的方式加入至框架中，使得组件甚至框架的整合变得容易。 Spring最为人重视的另一方面是支持AOP（Aspect-Oriented Programming）， 这次发布的Spring Security-3.0.1 是一个bug fix 版，主要是对3.0 中存在的一些问题进行修正。文档中没有添加新功能的介绍，但是将之前拼写错误的一些类名进行了修正，建议开发者以这一版本的文档为参考。 另：Spring Security 从2010-01-01 以后，版本控制从SVN 换成了GIT，我们在翻译文档的时候，主要是根据SVN 的变化来进行文档内容的比对，这次换成GIT 后，感觉缺少了之前 那种文本比对工具，如果有对GIT 熟悉的朋友，还请推荐一下文本比对的工具，谢谢。 序言 I. 入门 1. 介绍 1.1. Spring Security 是什么？ 1.2. 历史 1.3. 发行版本号 1.4. 获得Spring Security 1.4.1. 项目模块 1.4.1.1. Core - spring-security-core.jar 1.4.1. 2. Web - spring-security-web.jar 1.4.1.3. Config - spring-security-config.jar 1.4.1.4. LDAP - spring-security-ldap.jar 1.4.1.5. ACL - spring-security-acl.jar 1.4.1.6. CAS - spring-security-cas-client.jar 1.4.1.7. OpenID - spring-security-openid.jar 1.4. 2. 获得源代码 2. Security 命名空间配置 2.1. 介绍 2.1.1. 命名空间的设计 2.2. 开始使用安全命名空间配置 2.2.1. 配置web.xml 2.2.2. 最小 ’ OpenDoc Series Spring开发指南 文档说明 参与人员： 作者联络 见权权权权权 xiaxin(at)https://www.doczj.com/doc/242571725.html, (at) 为email @ 符号 发布记录 版本日期作者说明 0.5 2004.6.1 夏昕第一预览版 0.6 2004.9.1 夏昕补充“持久层”内容。 OpenDoc版权说明 本文档版权归原作者所有。 在免费、且无任何附加条件的前提下，可在网络媒体中自由传播。 如需部分或者全文引用，请事先征求作者意见。 如果本文对您有些许帮助，表达谢意的最好方式，是将您发现的问题和文档改进意见及时反馈给作者。当然，倘若有时间和能力，能为技术群体无偿贡献自己的所学为最好的回馈。 另外，笔者近来试图就日本、印度的软件开发模式进行一些调研。如果诸位可以赠阅日本、印度软件研发过程中的需求、设计文档以供研究，感激不尽！ Spring开发指南 前言 2003年年初，笔者在国外工作。其时，一位与笔者私交甚好的印度同事Paradeep从公司离职去斯坦福深造，临走送给笔者一本他最钟爱的书籍作为纪念。 工作间隙，时常见到他摩娑此书，摇头不止（印度人习惯和中国人相反，摇头代表肯定、赞同，相当于与中国人点头。笔者刚开始与印度同僚共事之时，每每组织项目会议，一屋子人频频摇头，让笔者倍感压力……J）。 下班后，带着好友离职的失落，笔者夹着这本书走在回家的路上，恰巧路过东海岸，天色依然明朗，随意坐上了海边一家酒吧的露天吧台，要了杯啤酒，随手翻弄着书的扉页，不经意看见书中遍布的钢笔勾画的线条。 “呵呵，Paradeep这家伙，还真把这本书当回事啊”，一边笑着，一边摊开了此书，想看看到底是怎样的书让这样一个聪明老练的同事如此欣赏。 从此开始，这本书伴随笔者度过了整整一个月的业余时间…….. 这本书，也就是出自Rod Johnson的： 《Expert One-on-One J2EE Design and Development》 此书已经由电子工业出版社出版，译版名为《J2EE设计开发编程指南》。 半年后，一个新的Java Framework发布，同样出自Rod Johnson的手笔，这自然引起了笔者极大的兴趣，这就是SpringFramework。 SpringFramework实际上是Expert One-on-One J2EE Design and Development一书中所阐述的设计思想的具体实现。在One-on-One一书中，Rod Johnson倡导J2EE实用主义的设计思想，并随书提供了一个初步的开发框架实现（interface21开发包）。而SpringFramework正是这一思想的更全面和具体的体现。Rod Johnson在interface21开发包的基础之上，进行了进一步的改造和扩充，使其发展为一个更加开放、清晰、全面、高效的开发框架。 本文正是针对SpringFramework的开发指南，讲述了SpringFramework的设计思想以及在开发中的实际使用。同时穿插了一些笔者在项目实作中的经验所得。Spring入门教程
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