解决could not initialize proxy - no Session

问题描述：

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.zhai.model.sys.Tresource.resources, could not initialize proxy - no Session

    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:575)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:214)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:554)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:142)
    at org.hibernate.collection.internal.PersistentSet.iterator(PersistentSet.java:180)
    at com.alibaba.fastjson.serializer.CollectionSerializer.write(CollectionSerializer.java:68)
    at com.alibaba.fastjson.serializer.JSONSerializer.writeWithFieldName(JSONSerializer.java:390)
    at Serializer_1.write1(Unknown Source)
    at Serializer_1.write(Unknown Source)
    at com.alibaba.fastjson.serializer.JSONSerializer.writeWithFieldName(JSONSerializer.java:390)
    at Serializer_1.write1(Unknown Source)
    at Serializer_1.write(Unknown Source)
    at com.alibaba.fastjson.serializer.JSONSerializer.write(JSONSerializer.java:361)
    at com.alibaba.fastjson.JSON.toJSONString(JSON.java:393)
    at com.alibaba.fastjson.JSON.toJSONString(JSON.java:381)
    at com.zhai.service.ResourceTest.getTreemenu(ResourceTest.java:29)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    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:73)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:82)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:73)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:224)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:83)
    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$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:68)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:163)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

导致出现该错误的代码：@ManyToMany(fetch = FetchType.LAZY) 采用了懒加载；

    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "sys_role_resource", joinColumns = { @JoinColumn(name = "resource_id", nullable = false, updatable = false) }, inverseJoinColumns = { @JoinColumn(name = "role_id", nullable = false, updatable = false) })
    @OrderBy("id ASC")
    public Set getRoles() {
        return roles;
    }

解决方法：
1、把lazy设成false。这个是最简单的办法，个人认为也是比较笨的方法。因为这是在用效率作为代价。

2、使用OpenSessionInViewFilter。这种方法是将session交给servlet filter来管理，每当一个请求来之后就会开

启一个session，只有当响应结束后才会关闭。如下：
在web.xml配置文件中加上该配置

<filter-name>hibernateFilterfilter-name>   
     <filter-class>  org.springframework.orm.hibernate3.support.OpenSessionInViewFilter filter-class>   
filter   
<filter-mapping>   
     <filter-name>hibernateFilterfilter-name>   
     /*   
filter-mapping> 

3、若是单纯的junit 测试的就只需加上 @Trantsactional

    @Autowired
    private ResourceServiceImpl resourceService;
    @Test
    @Transactional
    public void getTreemenu() {
        List l = null;
        l = resourceService.getTremenu(false);
        for (Tresource t : l) {
            System.out.println(JSONArray.toJSONString(t));
        }
    }
}