问题描述
在通过Hibernate查询Bean信息时报以下异常信息：
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org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:132)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:174)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)
at com.test.model.User_$$_javassist_0.toString(User_$$_javassist_0.java)
at java.lang.String.valueOf(String.java:2854)
at java.io.PrintStream.println(PrintStream.java:821)
at com.test.juniTest.otherTest.findUserById(otherTest.java:91)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
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分析：这错误很常见，字面意义就是不能被初始化，因为session已经关闭了。简单理解就是因为，你使用了lazy=true，这样hibernate在从数据库中调数据的时候是不会把关联的对象查出来的，而是保存一个获取值得方法，在你使用getXXX()调用的时候，hiberante会利用这个保存的方法去从数据库中取数据。而往往我们在jsp页面中使用getXXX()准备展示数据的时候，session早已经在dao中就关闭了，如果是实体Bean是通过注解模式被注入的（配置模式不再此文讨论范围内），则解决方法如下：
测试类：
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"file:WebContent/WEB-INF/applicationContext2.xml"})
public class otherTest{
@Autowired
private HibernateTemplate hibernateTemplate;
// 必须设置set方法
public void setHibernateTemplate(HibernateTemplate hibernateTemplate) {
this.hibernateTemplate = hibernateTemplate;
}
//通过id查询指定用户
//注意：需在User设置@org.hibernate.annotations.Proxy(lazy = false)
@Test
public void findUserById(){
User u= hibernateTemplate.load(User.class, 31);
System.out.println(u);//User [id=31, username=王大大3, password=111, email=wql025@sina.com]
}
}
实体Bean
@Entity
@Table(name="t_user")
@org.hibernate.annotations.Proxy(lazy = false)//设置立即加载
public class User {
private int id;
private String username;
private String password;
private String email;
@GeneratedValue
@Id
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@NotEmpty(message="用户名不能为空")
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
@Size(min=1,max=10,message="密码的长度应该在1和10之间")
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Email(message="邮箱格式不正确")
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public User(String username, String password, String email) {
super();
this.username = username;
this.password = password;
this.email = email;
}
public User(){}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password="
+ password + ", email=" + email + "]";
}
}
附：如果是配置模式，解决方法参考下文：
http://blog.csdn.net/s_good/article/details/7411642
鸣谢：http://bbs.csdn.net/topics/390522138