本文介绍了JPA的FetchType.LAZY为什么不起作用?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
JPA提供者eclipselink 2.3AS玻璃鱼3.1.1 B12远程调用Hessian的二进制协议
JPA provider eclipselink 2.3AS glassfish 3.1.1 B12Binary protocol for remote invocation Hessian
服务器端ejb + jpa客户端Plain Swing.
Server side ejb+jpaClient side Plain Swing .
JPA映射
@Entity
@Table(name = "FATHER", catalog = "CAT", schema = "dbo")
public class Father implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(generator = "FATHERUID", strategy = GenerationType.TABLE)
@TableGenerator(name = "FATHERUID", table = "FAMILY_UID", catalog = "LSDB", schema = "dbo", pkColumnName = "PRIM", pkColumnValue = "father_uid", valueColumnName = "UID", allocationSize = 1, initialValue = 0)
private Long id;
@OneToOne(mappedBy = "father", fetch = FetchType.LAZY)
private Mother mother;
@OneToMany(mappedBy = "father", fetch = FetchType.LAZY)
private List<Friend> friendList;
}
@Entity
@Table(name = "FRIEND", catalog = "CAT", schema = "dbo")
@NamedQueries({
@NamedQuery(name = "Friend.findAll", query = "SELECT f FROM Friend f")})
public class Friend implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(generator = "FRIENDUID", strategy = GenerationType.TABLE)
@TableGenerator(name = "FRIENDUID", table = "FAMILY_UID", catalog = "LSDB", schema = "dbo", pkColumnName = "PRIM", pkColumnValue = "friend_uid", valueColumnName = "UID", allocationSize = 1, initialValue = 0)
private Long id;
@JoinColumn(name = "FATHERID", referencedColumnName = "ID")
@ManyToOne(optional = false,fetch= FetchType.LAZY)
private Father father;
}
EJB方法
public Father findFather(long id) {
Father fath = em.find(Father.class, id);
PersistenceUnitUtil util = em.getEntityManagerFactory().getPersistenceUnitUtil();
System.out.println("mother isloaded="+util.isLoaded(fath,"mother"));
System.out.println("friendList isloaded="+util.isLoaded(fath,"friendList"));
return fath;
}
黑森州的客户端呼叫
public void findFather() {
try {
IManager manager = ProxyHelper.getStub();
//find by father id
Father father = manager.findFather(3500L);
System.out.println("Father=" + father);
System.out.println("father's friends=" + father.getFriendList());
System.out.println("mother=" + father.getMother());
} catch (MalformedURLException ex) {
}
}
一切正常，但是当查看服务器日志和父实体相关方时，我发现从数据库填充了LazyLoaded带注释的字段.
everything works fine, but when view server log and Father entity related parties I discoveredthat LazyLoaded anotated fields is filled from database.
服务器日志
FINEST: Begin deploying Persistence Unit test; session file:/C:/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test; state Predeployed; factoryCount 1
INFO: Instantiated an instance of org.hibernate.validator.engine.resolver.JPATraversableResolver.
FINEST: property=eclipselink.target-server; value=SunAS9; translated value=org.eclipse.persistence.platform.server.sunas.SunAS9ServerPlatform
FINEST: property=eclipselink.logging.level; value=FINEST; translated value=FINEST
FINEST: property=eclipselink.logging.parameters; value=true
FINEST: property=eclipselink.logging.level; value=FINEST; translated value=FINEST
FINEST: property=eclipselink.logging.parameters; value=true
FINEST: property=eclipselink.cache.shared.default; value=false; translated value=false
INFO: EclipseLink, version: Eclipse Persistence Services - 2.3.2.v20111125-r10461
FINEST: Database platform: org.eclipse.persistence.platform.database.oracle.Oracle11Platform, regular expression: (?i)oracle.*11
FINEST: Database platform: org.eclipse.persistence.platform.database.oracle.Oracle10Platform, regular expression: (?i)oracle.*10
FINEST: Database platform: org.eclipse.persistence.platform.database.oracle.Oracle9Platform, regular expression: (?i)oracle.*9
FINEST: Database platform: org.eclipse.persistence.platform.database.oracle.OraclePlatform, regular expression: (?i)oracle.*
FINEST: Database platform: org.eclipse.persistence.platform.database.SQLAnywherePlatform, regular expression: SQL\ Anywhere.*
FINEST: Database platform: org.eclipse.persistence.platform.database.SybasePlatform, regular expression: (?i)(sybase.*)|(adaptive\ server\ enterprise.*)|(SQL\ Server.*)
FINEST: Database platform: org.eclipse.persistence.platform.database.SQLServerPlatform, regular expression: (?i)microsoft.*
FINE: Detected database platform: org.eclipse.persistence.platform.database.SQLServerPlatform
CONFIG: connecting(DatabaseLogin(
platform=>DatabasePlatform
user name=> ""
connector=>JNDIConnector datasource name=>null
))
CONFIG: Connected: jdbc:jtds:sqlserver:
User: user
Database: Microsoft SQL Server Version: 10.50.1600
Driver: jTDS Type 4 JDBC Driver for MS SQL Server and Sybase Version: 1.2.5
FINEST: Connection acquired from connection pool [read].
FINEST: Connection released to connection pool [read].
CONFIG: connecting(DatabaseLogin(
platform=>SQLServerPlatform
user name=> ""
connector=>JNDIConnector datasource name=>null
))
CONFIG: Connected: jdbc:jtds:sqlserver:
User: user
Database: Microsoft SQL Server Version: 10.50.1600
Driver: jTDS Type 4 JDBC Driver for MS SQL Server and Sybase Version: 1.2.5
FINEST: sequencing connected, state is Preallocation_Transaction_NoAccessor_State
FINEST: sequence child_uid: preallocation size 1
FINEST: sequence friend_uid: preallocation size 1
FINEST: sequence father_uid: preallocation size 1
FINEST: sequence mother_uid: preallocation size 1
INFO: file:/C:/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test login successful
WARNING: Multiple [2] JMX MBeanServer instances exist, we will use the server at index [0] : [com.sun.enterprise.v3.admin.DynamicInterceptor@266bad10].
FINER: JMX MBeanServer instance found: [com.sun.enterprise.v3.admin.DynamicInterceptor@266bad10], # of beans: [21], domain: [DefaultDomain] at index: [0].
WARNING: JMX MBeanServer in use: [com.sun.enterprise.v3.admin.DynamicInterceptor@266bad10] from index [0]
FINER: JMX MBeanServer instance found: [com.sun.jmx.mbeanserver.JmxMBeanServer@6f7adf19], # of beans: [24], domain: [DefaultDomain] at index: [1].
WARNING: JMX MBeanServer in use: [com.sun.jmx.mbeanserver.JmxMBeanServer@6f7adf19] from index [1]
FINEST: Registered MBean: org.eclipse.persistence.services.mbean.MBeanDevelopmentServices[TopLink:Name=Development-file_/C_/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test,Type=Configuration] on server com.sun.jmx.mbeanserver.JmxMBeanServer@6f7adf19
FINEST: Registered MBean: org.eclipse.persistence.services.glassfish.MBeanGlassfishRuntimeServices[TopLink:Name=Session(file_/C_/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test)] on server com.sun.jmx.mbeanserver.JmxMBeanServer@6f7adf19
FINEST: EclipseLink JMX Runtime Services is referencing the [Platform ConversionManager] ClassLoader at: [WebappClassLoader (delegate=true; repositories=WEB-INF/classes/)]
FINEST: The applicationName for the MBean attached to session [file:/C:/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test] is [unknown]
FINEST: The moduleName for the MBean attached to session [file:/C:/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test] is [unknown]
FINER: Canonical Metamodel class [org.dima.model.Child_] not found during initialization.
FINER: Canonical Metamodel class [org.dima.model.Friend_] not found during initialization.
FINER: Canonical Metamodel class [org.dima.model.Father_] not found during initialization.
FINER: Canonical Metamodel class [org.dima.model.Mother_] not found during initialization.
FINEST: End deploying Persistence Unit test; session file:/C:/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test; state Deployed; factoryCount 1
FINER: client acquired: 50658177
FINER: TX binding to tx mgr, status=STATUS_ACTIVE
FINER: acquire unit of work: 1008456627
FINEST: Execute query ReadObjectQuery(name="readObject" referenceClass=Father sql="SELECT ID, NAME, SURNAME FROM LSDB.dbo.FATHER WHERE (ID = ?)")
FINEST: Connection acquired from connection pool [read].
FINEST: reconnecting to external connection pool
FINE: SELECT ID, NAME, SURNAME FROM LSDB.dbo.FATHER WHERE (ID = ?)
bind => [3500]
FINEST: Connection released to connection pool [read].
INFO: mother isloaded=false
INFO: friendList isloaded=false
FINER: TX beforeCompletion callback, status=STATUS_ACTIVE
FINER: begin unit of work commit
FINER: TX afterCompletion callback, status=COMMITTED
FINER: end unit of work commit
FINER: release unit of work
FINER: client released
FINEST: Execute query ReadAllQuery(name="file:/C:/netbeans/projects/JPATestServer/build/web/WEB-INF/classes/_test" referenceClass=Friend )
FINEST: Connection acquired from connection pool [read].
FINEST: reconnecting to external connection pool
**FINE: SELECT ID, NAME, SURNAME, FATHERID FROM LSDB.dbo.FRIEND WHERE (FATHERID = ?)
bind => [3500]**
FINEST: Connection released to connection pool [read].
FINEST: Register the existing object org.dima.model.Friend[ id=17496 ]
FINEST: Register the existing object org.dima.model.Friend[ id=17497 ]
FINEST: Register the existing object org.dima.model.Friend[ id=17498 ]
FINEST: Register the existing object org.dima.model.Friend[ id=17499 ]
FINEST: Register the existing object org.dima.model.Friend[ id=17500 ]
JPA提供程序为何执行此操作从LSDB.dbo.FRIEND WHERE中选择ID，NAME，SURNAME，FATHERID(FATHERID =?) 绑定=> [3500]
Why JPA provider executes thisSELECT ID, NAME, SURNAME, FATHERID FROM LSDB.dbo.FRIEND WHERE (FATHERID = ?) bind => [3500]
有什么主意吗?
推荐答案
默认情况下，仅在Java SE环境中对xToMany关系执行延迟加载(因为EclipseLink可以在使用集合的地方使用IndirectList).如果要延迟加载xToOne关系，则必须使用类编织.
Lazy loading is only done for xToMany relation in a Java SE environment by default (since EclipseLink can use IndirectList where collections are used). If you want to lazy load xToOne relations you have to use class weaving.
这篇关于JPA的FetchType.LAZY为什么不起作用?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！