java - 拦截器抛出的异常不会转到异常处理程序。

Question

我今天遇到了一个问题。我有一个开始并提交 Hibernate 事务的拦截器，它可能会在提交时抛出异常(例如 org.hibernate.StaleObjectStateException)。也就是说，它可以抛出异常，但异常不会到达处理程序。我认为我的代码有问题。但后来我写了一个简单的测试，就在这里

struts.xml中的包定义:

<package name="basicstruts2" namespace="/" extends="struts-default">
    <interceptors>
        <interceptor name="dummy" class="test.TestInterceptor"/>

        <interceptor-stack name="myStack">
            <interceptor-ref name="defaultStack" />
            <interceptor-ref name="dummy" />
        </interceptor-stack>
    </interceptors>

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

    <global-results>
        <result name="exception" type="chain">exceptionHandler</result>
    </global-results>

    <global-exception-mappings>
        <exception-mapping exception="java.lang.Exception" result="exception" />
    </global-exception-mappings>

    <action name="test" class="test.TestAction">
        <result>result.jsp</result>
    </action>

    <action name="exceptionHandler" class="test.ExceptionHandler">
        <result>DebugErrorPage.jsp</result>
    </action>
</package>

TestAction.java:

package test;

public class TestAction extends ActionSupport {

    private BusinessLogic logic = new BusinessLogic();

    public String execute() {
        logic.test();
        return SUCCESS;
    }
}

TestInterceptor.java:

package test;

public class TestInterceptor implements Interceptor {

    @Override
    public String intercept(ActionInvocation arg0) throws Exception {
        String result = null;
        try {
            result = arg0.invoke();
            boolean flag = true;
            if (flag) throw new RuntimeException("qwerty");
        } catch (Exception e) {
            System.out.println("exception catched in interceptor, rethrowing " + e);
            throw e;
        }
        return result;
    }

}

ExceptionHandler.java:

package test;

public class ExceptionHandler extends ActionSupport {

    private Exception exception;

    public void setException(Exception e) {
        exception = e;
        System.out.println("setting exception");
    }

    public String execute() {
        System.out.println("exeption in handler " + exception);
        return SUCCESS;
    }

}

BusinessLogic.java:

package test;

public class BusinessLogic {
    public void test() {
        System.out.println("test logic");
//      boolean flag = true;
//      if (flag) throw new RuntimeException("qwerty");
    }
}

所以，控制台输出:

test logic
exception catched in interceptor, rethrowing java.lang.RuntimeException: qwerty

但是如果 BusinnesLogic 抛出异常，我们可以取消注释代码:

BusinessLogic.java:

package test;

public class BusinessLogic {
    public void test() {
        System.out.println("test logic");
        boolean flag = true;
        if (flag) throw new RuntimeException("qwerty");
    }
}

并注释掉拦截器中的代码:

@Override
        public String intercept(ActionInvocation arg0) throws Exception {
            String result = null;
            try {
            result = arg0.invoke();
        //  boolean flag = true;
        //  if (flag) throw new RuntimeException("qwerty");
            } catch (Exception e) {
                System.out.println("exception catched in interceptor, rethrowing " + e);
                throw e;
            }
            return result;
        }

输出将是:

test logic
exception catched in interceptor, rethrowing java.lang.RuntimeException: qwerty
setting exception
exeption in handler java.lang.RuntimeException: qwerty

我们将看到错误页面。

那么，有人可以对这种行为给出一个很好的解释吗？如果异常拦截器无法处理其他拦截器抛出的异常，那么将异常拦截器放在默认 struts 堆栈的顶部有什么意义呢？为什么？如果您能提供一个好的答案，我将不胜感激。

编辑:有一个代码我有问题:

public String intercept(ActionInvocation arg0) throws Exception {
    String result = null;

    try {

        sf.getCurrentSession().beginTransaction();

        result = arg0.invoke();

        sf.getCurrentSession().getTransaction().commit();

    } catch (StaleObjectStateException staleEx) {
        if (sf.getCurrentSession().getTransaction().isActive()) {
            sf.getCurrentSession().getTransaction().rollback();
        }
        throw staleEx;

    } catch (Exception ex) {
        ex.printStackTrace();
        try {
            if (sf.getCurrentSession().getTransaction().isActive()) {
                sf.getCurrentSession().getTransaction().rollback();
            }
        } catch (Throwable rbEx) {
        }

        // Let others handle it... maybe another interceptor for exceptions?
        throw new ServletException(ex);
    }

    return result;
}

如果我想处理在 commit() 上抛出的异常，应该怎么做？

Answer 1

异常由 TestInterceptor 在操作调用和结果呈现之后抛出。

来自 Writing Interceptors page 上的注释:

Keep in mind that invoke will return after the result has been called (eg. after you JSP has been rendered), making it perfect for things like open-session-in-view patterns. If you want to do something before the result gets called, you should implement a PreResultListener.