java - 如何在 Spring Data 中延迟加载集合？

Question

我有一个对象模型

@Table(name = "MOB_Objects")
public class ak_BankObject {
// private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE)
private long id;

public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

@ManyToOne
private ak_Zones ak_zone;

@OneToMany(cascade = CascadeType.ALL)
/* (mappedBy="brfebranchid") */
@JoinTable(name = "mob_bankObj_branchF")
List<ak_BranchFeatures> ak_branchFeatures;

@OneToMany(cascade = CascadeType.ALL)
@JoinTable(name = "mob_bankObj_image")
List<ak_BranchImages> ak_branchImages;

@OneToMany
List<ak_BranchScore> BranchScore;

@OneToMany
List<ak_BranchComment> BranchComment;

@Column
private Integer objectid;

@Column
private String branchname;

@Column
private String branchcode;

@Column
private Integer branchtype;

@Column
private String branchchief;

@Column
private String postalcode;

@Column
private Integer branchdegree;

@Column
private String branchtel;

@Column
private String branchfax;

@Column
private String branchtelbank;

@Column
private String address;

@Column
private Integer objecttype;

@Column
private double latitude;

@Column
private double longitude;

@Column
private String codedevices;

public ak_Zones getAk_zone() {
    return ak_zone;
}

public void setAk_zone(ak_Zones ak_zone) {
    this.ak_zone = ak_zone;
}

public List<ak_BranchFeatures> getAk_branchFeatures() {
    return ak_branchFeatures;
}

public void setAk_branchFeatures(List<ak_BranchFeatures> ak_branchFeatures) {
    this.ak_branchFeatures = ak_branchFeatures;
}

public String getBranchname() {
    return branchname;
}

public void setBranchname(String branchname) {
    this.branchname = branchname;
}

public String getBranchcode() {
    return branchcode;
}

public void setBranchcode(String branchcode) {
    this.branchcode = branchcode;
}

public Integer getBranchtype() {
    return branchtype;
}

public void setBranchtype(Integer branchtype) {
    this.branchtype = branchtype;
}

public String getBranchchief() {
    return branchchief;
}

public void setBranchchief(String branchchief) {
    this.branchchief = branchchief;
}

public String getPostalcode() {
    return postalcode;
}

public void setPostalcode(String postalcode) {
    this.postalcode = postalcode;
}

public Integer getBranchdegree() {
    return branchdegree;
}

public void setBranchdegree(Integer branchdegree) {
    this.branchdegree = branchdegree;
}

public String getBranchtel() {
    return branchtel;
}

public void setBranchtel(String branchtel) {
    this.branchtel = branchtel;
}

public String getBranchfax() {
    return branchfax;
}

public void setBranchfax(String branchfax) {
    this.branchfax = branchfax;
}

public String getBranchtelbank() {
    return branchtelbank;
}

public void setBranchtelbank(String branchtelbank) {
    this.branchtelbank = branchtelbank;
}

public String getAddress() {
    return address;
}

public void setAddress(String address) {
    this.address = address;
}

public Integer getObjecttype() {
    return objecttype;
}

public void setObjecttype(Integer objecttype) {
    this.objecttype = objecttype;
}

public Integer getObjectid() {
    return objectid;
}

public void setObjectid(Integer objectid) {
    this.objectid = objectid;
}

public String getCodedevices() {
    return codedevices;
}

public void setCodedevices(String codedevices) {
    this.codedevices = codedevices;
}

public double getLatitude() {
    return latitude;
}

public void setLatitude(double latitude) {
    this.latitude = latitude;
}

public double getLongitude() {
    return longitude;
}

public void setLongitude(double longitude) {
    this.longitude = longitude;
}

public List<ak_BranchComment> getBranchComment() {
    return BranchComment;
}

public void setBranchComment(List<ak_BranchComment> branchComment) {
    BranchComment = branchComment;
}

public List<ak_BranchScore> getBranchScore() {
    return BranchScore;
}

public void setBranchScore(List<ak_BranchScore> branchScore) {
    BranchScore = branchScore;
}

public List<ak_BranchImages> getAk_branchImages() {
    return ak_branchImages;
}

public void setAk_branchImages(List<ak_BranchImages> ak_branchImages) {
    this.ak_branchImages = ak_branchImages;
}

@Override
public String toString() {
    return "BankObject [id=" + id + ", lon=" + longitude + ", latitude="
            + latitude + "]";
}}

我的存储库:

public interface BankRepository extends CrudRepository<ak_BankObject, Long> {}

我的服务:

@Service
public class BankService {
public List<ak_BankObject> searchInBbox(double minLon, double minLat, double maxLon,
            double maxLat) {

        List<ak_BankObject> banks = (List<ak_BankObject>) bankRepository.findAll();
        List<ak_BankObject> inBoxBanks = new ArrayList<>();

        for (int i = 0; i < banks.size(); i++) {
            double lon = banks.get(i).getLongitude();
            double lat = banks.get(i).getLatitude();
            if (lon >= minLon && lon <= maxLon && lat >= minLat
                    && lat <= maxLat) {
                inBoxBanks.add(banks.get(i));
            }
        }
        return inBoxBanks;
    }}

使用 spring 数据，我使用 crudRepository 来查找该对象中的所有内容，但出现错误:

SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/MBFinder] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.spr.model.ak_BankObject.ak_branchFeatures, could not initialize proxy - no Session] with root cause
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.spr.model.ak_BankObject.ak_branchFeatures, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:566)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:186)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:545)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:124)
    at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:500)
    at java.lang.String.valueOf(Unknown Source)
    at java.lang.StringBuilder.append(Unknown Source)
    at com.spr.model.ak_BankObject.toString(ak_BankObject.java:272)
    at java.lang.String.valueOf(Unknown Source)
    at java.lang.StringBuilder.append(Unknown Source)
    at java.util.AbstractCollection.toString(Unknown Source)
    at java.lang.String.valueOf(Unknown Source)
    at java.lang.StringBuilder.append(Unknown Source)
    at com.spr.controller.BankController.searchNearest(BankController.java:42)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:183)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.session.ConcurrentSessionFilter.doFilter(ConcurrentSessionFilter.java:125)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

我不想使用 EAGER，但我看到了 this Solution但对我不起作用，有没有办法代替 native 查询？

Answer 1

因为当您在惰性端获取属性时， session 已关闭。因此您无法获取该属性，并且您将收到异常。

为您提供 3 个解决方案:

1. 将 fetch 属性更改为 fetch = FetchType.EAGER。
2. 通过代码控制 session 范围。意味着在完成所有操作后，从获取属性开始打开 session ，然后在finally block 中将其关闭。
3. 如果您的APP是Web应用，请使用OpenSessionInView过滤器自动控制 session 范围。