1.我定义Survey和Page类,Survey设置Page的集合属性,然后建立双向关联,我故意把集合注解成懒加载...
2.然后我通过这段代码把Page集合重数据库取出
3.然后调用Survey的get方法得到集合,再把Page一个一个放进集合中去
4.然后再外面迭代Survey的page集合抛异常是懒加载
为什么？为什么？为什么？
/*
*通过survey的id取出survey
*(我用spring在这方法上面配置了事务)
*/
public Survey findByid(int id){
Survey survey = surveyDaoImp.getEntity(id);
String hql = "from Page p where p.survey.id=? order by p.id desc";
List<Page> list = pageDaoImp.findEntityByHQL(hql, id);
for(Page page : list){
survey.getPages().add(page);
}
return survey;
}
我的测试方法
@Test
public void test3(){
BeanFactory a = new ClassPathXmlApplicationContext("beans.xml");
SurveyService s = (SurveyService) a.getBean("surveyService");
Survey survey = s.findByid(40);
for(Page page : survey.getPages()){
System.out.println(page.getTitle()+":"+page.getId());
}
}
下面是2个javabean
@Entity
public class Survey {
private int id;
private String title="未命名";
private String preText="上一步";
private String nextText="下一步";
private String exitText="退出";
private String doneText="完成";
private Date createTime = new Date();
private Users users;
private List<Page> pages = new ArrayList<Page>();
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getPreText() {
return preText;
}
public void setPreText(String preText) {
this.preText = preText;
}
public String getNextText() {
return nextText;
}
public void setNextText(String nextText) {
this.nextText = nextText;
}
public String getExitText() {
return exitText;
}
public void setExitText(String exitText) {
this.exitText = exitText;
}
public String getDoneText() {
return doneText;
}
public void setDoneText(String doneText) {
this.doneText = doneText;
}
public Date getCreateTime() {
return createTime;
}
public void setCreateTime(Date createTime) {
this.createTime = createTime;
}
@ManyToOne
@JoinColumn(name="users_id")
public Users getUsers() {
return users;
}
public void setUsers(Users users) {
this.users = users;
}
@OneToMany(mappedBy="survey", cascade=CascadeType.ALL)
public List<Page> getPages() {
return pages;
}
public void setPages(List<Page> pages) {
this.pages = pages;
}
}
@Entity
public class Page {
private int id;
private String title = "未命名";
private String description;
private Survey survey;
private List<Question> questions = new ArrayList<Question>();
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@ManyToOne
@JoinColumn(name="survey_id")
public Survey getSurvey() {
return survey;
}
public void setSurvey(Survey survey) {
this.survey = survey;
}
@OneToMany(mappedBy="page", fetch=FetchType.EAGER)
public List<Question> getQuestions() {
return questions;
}
public void setQuestions(List<Question> questions) {
this.questions = questions;
}
}
**这是日志的sql语句**
Hibernate:
select
survey0_.id as id2_1_,
survey0_.createTime as createTime2_1_,
survey0_.doneText as doneText2_1_,
survey0_.exitText as exitText2_1_,
survey0_.nextText as nextText2_1_,
survey0_.preText as preText2_1_,
survey0_.title as title2_1_,
survey0_.users_id as users8_2_1_,
from
Survey survey0_
where
survey0_.id=?
Hibernate:
select
page0_.id as id0_,
page0_.description as descript2_0_,
page0_.survey_id as survey4_0_,
page0_.title as title0_
from
Page page0_
where
page0_.survey_id=?
order by
page0_.id desc
这是抛出的异常
016-2-6 22:26:24 org.hibernate.LazyInitializationException
严重: failed to lazily initialize a collection of role: zhang.model.Survey.pages, no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: zhang.model.Survey.pages, no session or session was closed
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380)
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:108)
at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:272)
at MyTest.test3(MyTest.java:44)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
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:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
