出现问题： 

SSH整合项目里，项目目录结构如下：

在EmployeeAction.java的list()方法里将employees的list放入到request的Map中。

EmployeeAction.java:

 package com.tt.ssh.actions;

 import java.util.Arrays;

 import java.util.Map;

 import org.apache.struts2.interceptor.RequestAware;

 import com.opensymphony.xwork2.ActionContext;

 import com.opensymphony.xwork2.ActionSupport;

 import com.opensymphony.xwork2.util.ValueStack;

 import com.tt.ssh.service.EmployeeService;

 public class EmployeeAction extends ActionSupport implements RequestAware{

     private static final long serialVersionUID = 1L;

     private EmployeeService employeeService;

     public void setEmployeeService(EmployeeService employeeService) {

         this.employeeService = employeeService;

     }

     Map<String, Object> request;

     public String list(){

         request.put("employees",employeeService.getAll());

         return "list";

     }

     @Override

     public void setRequest(Map<String, Object> arg0) {

         // TODO Auto-generated method stub

         this.request = arg0;

     }

 }

然后到emp-list.jsp页面上进行获取，发现始终都获取不到employees。

emp-list.jsp:

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

 <title>Insert title here</title>

 </head>

 <body>

        <s:debug></s:debug>

        <center>

            <h4>list页面显示成功！</h4>

            <s:if test="#request.employees == null || #request.employees.size() == 0">

                  没有任何员工信息

            </s:if>

            <s:else>

                 <table border="1" cellpadding="10" cellspacing="0">

                     <s:iterator value="#request.employees" var="employee">

                         <tr>

                           <td>${employee.id }</td>

                           <td>${employee.lastName }</td>

                           <td>${employee.email }</td>

                           <td>${employee.birth }</td>

                           <td>${employee.createTime }</td>

                           <td>${employee.department.deptName }</td>

                         </tr>

                     </s:iterator>

                 </table>

            </s:else>

        </center>

 </body>

 </html>

排除jsp页面问题，于是进入怀疑在EmployeeAction里employees的list压根没放成功。

运行到第25行就报错，同时从ctx获取ContextMap进而获取request的Map时得到的为null,这说明employees的list确实没有放入到request的Map中。

报错如下：

Stacktraces

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

    org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:164)

    org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:285)

    org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)

    com.tt.ssh.entities.Department_$$_javassist_1.toString(Department_$$_javassist_1.java)

    java.lang.String.valueOf(String.java:2994)

    java.lang.StringBuilder.append(StringBuilder.java:131)

    com.tt.ssh.entities.Employee.toString(Unknown Source)

    java.lang.String.valueOf(String.java:2994)

    java.lang.StringBuilder.append(StringBuilder.java:131)

    java.util.AbstractCollection.toString(AbstractCollection.java:462)

    com.tt.ssh.actions.EmployeeAction.list(Unknown Source)

    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

    java.lang.reflect.Method.invoke(Method.java:498)

    ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:871)

    ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1294)

    ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)

    com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:117)

    com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:108)

    ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1370)

    ognl.ASTMethod.getValueBody(ASTMethod.java:91)

    ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)

    ognl.SimpleNode.getValue(SimpleNode.java:258)

    ognl.Ognl.getValue(Ognl.java:467)

    ognl.Ognl.getValue(Ognl.java:431)

    com.opensymphony.xwork2.ognl.OgnlUtil$3.execute(OgnlUtil.java:352)

    com.opensymphony.xwork2.ognl.OgnlUtil.compileAndExecuteMethod(OgnlUtil.java:404)

    com.opensymphony.xwork2.ognl.OgnlUtil.callMethod(OgnlUtil.java:350)

    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:430)

    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:290)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:251)

    org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:168)

    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)

    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:76)

    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)

    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)

    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:125)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:253)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)

    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:140)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)

    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)

    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)

    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:575)

    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81)

    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)

    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)

    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)

    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)

    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)

    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)

    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)

    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)

    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)

    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)

    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)

    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1100)

    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:687)

    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2508)

    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2497)

    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

    java.lang.Thread.run(Thread.java:745)

 

 分析原因：

  EmployeeService.java:

 package com.tt.ssh.service;

 import java.util.List;

 import com.tt.ssh.dao.EmployeeDao;

 import com.tt.ssh.entities.Employee;

 public class EmployeeService {

     private EmployeeDao employeeDao;

     public void setEmployeeDao(EmployeeDao employeeDao) {

         this.employeeDao = employeeDao;

     }

     public List<Employee> getAll(){

         return employeeDao.getAll();

     }

 }

而EmployeeDao.java:

 package com.tt.ssh.dao;

 import java.util.List;

 import org.hibernate.Session;

 import org.hibernate.SessionFactory;

 import com.tt.ssh.entities.Employee;

 public class EmployeeDao {

     private SessionFactory sessionFactory;

     public void setSessionFactory(SessionFactory sessionFactory) {

         this.sessionFactory = sessionFactory;

     }

     public Session getSession(){

         return this.sessionFactory.getCurrentSession();

     }

     public List<Employee> getAll(){

         String hql = "FROM Employee";

         return getSession().createQuery(hql).list();

     }

 }

可以看到，employee的list是从Hibernate的session里获取的。

报错是一个懒加载异常，意识是在session（hibernate里的session）关闭后使用employee对象的未加载变量，也就是说session已经关闭，然而该实例变量却还没有被初始化，就使用了该实例变量，导致该异常。

applicationContext.xml配置如下：


由于employee是由hibernate进行加载的，可能hibernate本身是以load的方式将该实例变量得到。此时在employeeDao里session获取到的是的employee代理类对象，整个Session范围内，应用程序没有访问过employee对象，那么employee代理类的实例一直不会被初始话。事务是作用在EmployeeService上，导致
List<Employee> getAll( )方法调用之前获取Session、开启事务，这个方法结束之后提交事务、关闭session。session关闭后，在EmployeeAction获取employee时是未初始化的employee代理类对象，未被初始化的代理类对象只有OID其他属性全为null，那么放入request的Map里的是未被初始化的employee代理类对象。一旦在action或者jsp里要获取employee代理类对象，必然会发生懒加载异常。同理，在jsp里获取employee的department时同样存在懒加载的问题。
(关于hiberante的延迟加载，更详细的在我的另一篇博客里：http://www.cnblogs.com/TTTTT/p/6682304.html)

解决办法：

方法1.用openSessionInView 。
方法2.把这个类的延迟加载禁掉，lazy设为false。
方法3.迫切左外连接。

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