如何实现 Hibernate 会话/事务拦截器以避免在 Struts 2 中执行 JSON 结果时出现 LazyInitializationException？

问题描述 投票：0回答：3

我正在尝试实现一个 Hibernate 会话/事务拦截器以避免 Struts 2 中 JSON 结果出现 

LazyInitializationException
，但我得到了这个异常：

245968 [http-8080-7] ERROR util.HibernateEndTransInterceptor  - org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:238)
    at org.apache.struts2.json.JSONWriter.processCustom(JSONWriter.java:171)
    at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:161)
    at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:127)
    at org.apache.struts2.json.JSONWriter.write(JSONWriter.java:95)
    at org.apache.struts2.json.JSONUtil.serialize(JSONUtil.java:116)
    at org.apache.struts2.json.JSONResult.createJSONString(JSONResult.java:196)
    at org.apache.struts2.json.JSONResult.execute(JSONResult.java:170)
    at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:374)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:278)
    at util.HibernateEndTransInterceptor.intercept(HibernateEndTransInterceptor.java:55)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:236)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:236)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:192)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at util.HibernateBeginTransInterceptor.intercept(HibernateBeginTransInterceptor.java:32)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at util.LoginInterceptor.intercept(LoginInterceptor.java:36)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:511)
    at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
    at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:831)
    at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:652)
    at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1203)
    at java.lang.Thread.run(Thread.java:722)
Caused by: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:238)
    at org.apache.struts2.json.JSONWriter.processCustom(JSONWriter.java:171)
    at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:161)
    at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:127)
    at org.apache.struts2.json.JSONWriter.add(JSONWriter.java:363)
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:223)
    ... 73 more
Caused by: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:238)
    at org.apache.struts2.json.JSONWriter.processCustom(JSONWriter.java:171)
    at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:161)
    at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:127)
    at org.apache.struts2.json.JSONWriter.add(JSONWriter.java:363)
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:223)
    ... 78 more
Caused by: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:238)
    at org.apache.struts2.json.JSONWriter.processCustom(JSONWriter.java:171)
    at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:161)
    at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:127)
    at org.apache.struts2.json.JSONWriter.add(JSONWriter.java:363)
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:223)
    ... 83 more
Caused by: java.lang.reflect.InvocationTargetException
    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:601)
    at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:218)
    ... 88 more
Caused by: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:165)
    at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:272)
    at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)
    at com.lm.model.common.Language_$$_javassist_0.getName(Language_$$_javassist_0.java)
    ... 93 more

我的拦截器看起来像这样：

package util;

import java.util.Map;

import org.apache.log4j.Logger;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

import util.hibernate.HibernateUtil;

import com.lm.action.ActionsConstants;
import com.lm.action.user.Constants;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.Interceptor;

public class HibernateEndTransInterceptor implements Interceptor, Constants, ActionsConstants {


    private static final long serialVersionUID = -8734958511612355789L;

    private static SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private transient Logger log = Logger.getLogger(HibernateEndTransInterceptor.class);
    private Session s=null;
    private Transaction t=null;

    @Override
    public void destroy() {
    }

    @Override
    public void init() {
    }

    @Override
    public String intercept(final ActionInvocation invocation) throws Exception {
        /*invocation.addPreResultListener(new PreResultListener() {
            
            @Override
            public void beforeResult(ActionInvocation arg0, String arg1) {
                Map<String, ResultConfig> resultsMap = invocation.getProxy().getConfig().getResults();
                //ResultConfig finalResultConfig = resultsMap.get(resultCode);
                
            }
        });*/

            
        Map<String,Object> strutsSession = invocation.getInvocationContext().getSession();
        String res=null;
        try {
            s=sessionFactory.openSession();
            t = s.beginTransaction();
            strutsSession.put("hibernateSession", s);
            strutsSession.put("hibernateTransaction", t);
            res=invocation.invoke();
            t.commit();
        } catch (Throwable t2) {
            log.error(t2,t2);
            try {
                t.rollback();
            } catch (Throwable t3) {
                log.error(t3,t3);
            }
        } finally {
            try {
                s.close();
            } catch (Throwable t) {
                log.error(t,t);
            }
            strutsSession.remove("hibernateSession");
            strutsSession.remove("hibernateTransaction");
        }
        return res;
    }

}

它不起作用。我什至在 

LazyInitializationException
和 
trans.commit()
 之前就得到了
session.close();

java json hibernate struts2 lazy-initialization
3个回答
1
投票

请勿重新实施威尔。如果您需要在视图概念中实现打开会话，请使用Hibernate Full Plugin。如果您想修复 

LazyInitializationException
，请将 
FetchType.EAGER
放在集合上。

1
投票

好吧，最后我解决了将通用 DAO（带有会话和事务）注入到 genericAction 的问题。 这适用于带有惰性休眠 bean 的 JSONResults 和 jsp。

感谢对“bmorris591”和“Roman C”的贡献（我不想要，甚至不需要所有这些插件）。

我留下我的例子，我希望我不会忘记任何事情......

拦截器配置（struts.xml片段）：

<package name="lmp" extends="struts-default,json-default">
    <interceptors>
        <interceptor name="login" class="util.LoginInterceptor"/>
        <interceptor name="hibernateSessionTransInjector" class="util.HibernateSessionTransInjectorInterceptor"/>
        <interceptor-stack name="loggingStack">
            <interceptor-ref name="login" />
            <interceptor-ref name="defaultStack" />
            <interceptor-ref name="hibernateSessionTransInjector"/>
        </interceptor-stack>
    </interceptors>

    <default-interceptor-ref name="loggingStack"/>

    <global-results>
        <result name="login" type="redirectAction">login</result>
    </global-results>
</package>
<package name="myAction" extends="lmp">

    <action name="myAction" class="com.lmp.MyAction">
        <result name="json" type="json">
            <param name="ignoreHierarchy">false</param>
        </result>
        <result name="*">/jsp/myAction.jsp</result>
    </action>
</package>

拦截器实现：

package util;

import org.apache.log4j.Logger;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

import util.hibernate.HibernateUtil;

import com.lm.action.ActionsConstants;
import com.lm.action.user.Constants;
import com.lm.dao.DAO;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.Interceptor;

public class HibernateSessionTransInjectorInterceptor implements Interceptor, Constants, ActionsConstants {


    private static final long serialVersionUID = -8734958511612355789L;

    private static SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private transient Logger log = Logger.getLogger(HibernateSessionTransInjectorInterceptor.class);

    @Override
    public void destroy() {
    }

    @Override
    public void init() {
    }

    @Override
    public String intercept(final ActionInvocation invocation) throws Exception {
        String res=null;
        DAO dao=null;
        try {
            Session s=sessionFactory.openSession();
            dao = new DAO(s);
            dao.beginTransaction();
            **invocation.getStack().setValue("dao", dao, true);**
            res=invocation.invoke();
            boolean rollback=(Boolean)invocation.getStack().findValue("rollbackTransaction", Boolean.class);
            if (rollback)
                dao.rollBackTransaction();
            if (!dao.getT().wasRolledBack())
                dao.commitTransaction();
        } catch (Throwable t2) {
            log.error(t2,t2);
            if (dao!=null)
            try {
                dao.rollBackTransaction();
            } catch (Throwable t3) {
                log.error(t3,t3);
            }
        } finally {
            if (dao!=null)
            try {
                dao.finallyClose();
            } catch (Throwable t) {
                log.error(t,t);
            }
        }
        return res;
    }

}

UserDAO 示例：

public class UserDAO extends DAO {

[...]
    public UserDAO(Session s) {
        super(s);
    }
[...]
}

通用DAO示例：

public class DAO {

    protected static final transient Logger log = Logger.getLogger(DAO.class);

    public static SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    public Session s = null;
    public Transaction t = null;

    public DAO(Session s) {
        this.s=s;
    }

    public void beginTransaction(Transaction t) {
        this.t=t;
    }

    private int exceptionErr=0;
    public void beginTransaction() {
        try {
            t=s.beginTransaction();
        } catch (Throwable t) {
            log.error(t,t);
        }
    }
    public void rollBackTransaction() {
        if (t!=null && t.isActive())
            t.rollback();
    }
    public void commitTransaction() {
        if (t!=null && t.isActive())
            t.commit();
    }

    public void finallyClose() {
        if (t!=null && t.isActive()) 
            t.rollback();
        if (s!=null && s.isOpen())
            s.close();
    }

    public Session getS() {
        return s;
    }

    public void setS(Session s) {
        this.s = s;
    }

    public Transaction getT() {
        return t;
    }

    public void setT(Transaction t) {
        this.t = t;
    }

}

通用操作：

public class GenericAction extends ActionSupport  {

    private DAO dao=null;  //Interceptor injects here

    public GenericAction() {
    }

...
    @JSON(deserialize=false, serialize=false)
    public DAO getDao() {
        return dao;
    }

    @JSON(deserialize=false, serialize=false)
    public void setDao(DAO dao) {
        this.dao = dao;
    }

}

我的行动：

public class MyAction extends GenericAction {

    public MyAction() {
    }

    @Override
    public String execute() throws Exception {
        super.execute();
        UserDAO userDAO=new UserDAO(getDao().getS());
        OtherDAO otherDAO=new OtherDAO(getDao().getS());
        userDAO.loadUsers(...);
            return SUCCESS;
    }
}
0
投票

如果这是一个 Struts2 拦截器，这绝对不是实现它的方式。

应用程序对于所有请求都有一个拦截器实例，因此一个请求正在 

intercept
方法中设置变量，然后另一个请求进入并在第一个请求仍在处理时重置它们。 然后，第一个请求会在第二个请求的会话上调用 
session.close()
时返回。

你的拦截器应该看起来更像这样：

@Override
public String intercept(final ActionInvocation invocation) throws Exception {
    final Map<String, Object> strutsSession = invocation.getInvocationContext().getSession();
    String res = null;
    Session s = null;
    Transaction t = null;
    try {
        s = sessionFactory.openSession();
        t = s.beginTransaction();
        strutsSession.put("hibernateSession", s);
        strutsSession.put("hibernateTransaction", t);
        res = invocation.invoke();
        t.commit();
    } catch (Throwable t2) {
        log.error(t2, t2);
        t.rollback();
    } finally {
        s.close();
        strutsSession.remove("hibernateSession");
        strutsSession.remove("hibernateTransaction");
    }
    return res;
}

请注意，所有变量都是本地变量，除非您希望它们在请求之间共享。

此外，最好的做法是扩展 

AbstractInterceptor
，这样您就不会拥有所有空方法。

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