struts2.0（30-40）-优快云博客

本文链接：https://blog.youkuaiyun.com/pingfanwuzhe/article/details/5582290

本文详细介绍了Struts2框架中的拦截器概念及其使用方法，包括如何创建自定义拦截器、配置拦截器栈、实现方法过滤拦截器以及利用监听器进行结果前的操作。

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拦截器：

package com.interceptor;

public class Interceptor

{

public void before()

{

System.out.println("before");

}

public void after()

{

System.out.println("after");

}

反射机制或处理类

package com.interceptor;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

public class MyHandler implements InvocationHandler

{

//定义目标对象

private Object object;

//声明拦截器对象

private Interceptor interceptor = new Interceptor();

//定义目标对象设置

public void setObject(Object object)

{

this.object = object;

}

/**

* invoke是真正执行的方法

public Object invoke(Object proxy, Method method, Object[] args)

throws Throwable

{

Object result = null;

interceptor.before();

result = method.invoke(object, args);//目标方法

interceptor.after();

return result;

}

代理类，最终是通过代理类来处理的

package com.interceptor;

import java.lang.reflect.Proxy;

/**

* 用于产生代理

* @author 向先函

public class MyProxy

{

//传入的是目标对象

public Object getProxy(Object object)

{

MyHandler myHandler = new MyHandler();

myHandler.setObject(object);

//返回新的代理，第一个参数是类的装载器，第二个参数是实现的接口，第三个参数是处理的实例

return Proxy.newProxyInstance(Target.class.getClassLoader(), object

.getClass().getInterfaces(), myHandler);

}

测试类：

package com.interceptor;

public class Client

{

public static void main(String[] args)

{

//目标对象，或被拦截的对象

TargetInterface target = new Target();

MyProxy myProxy = new MyProxy();

//生成代理代理目标对象

TargetInterface proxy = (TargetInterface)myProxy.getProxy(target);

proxy.doSomething();

}

Struts拦截器（主要用来拦截action）

建立拦截器

package com.test.interceptor;

import com.opensymphony.xwork2.ActionInvocation;

import com.opensymphony.xwork2.interceptor.Interceptor;

public class MyInterceptor implements Interceptor

{

public void destroy()

{

System.out.println("destroy");

}

public void init()

{

System.out.println("init");

}

public String intercept(ActionInvocation invocation) throws Exception

{

System.out.println("intercept");

String result = invocation.invoke();

System.out.println("finish");

return result;

}

配置struts.xml

<param name="hello">world</param>

</interceptor>

</interceptors>

<result name="success">/success.jsp</result>

<result name="input">/register2.jsp</result>

<interceptor-ref name="myInterceptor">

</interceptor-ref>

</action>

Struts2的核心是拦截器

以上代码运行拦截成功，但默认拦截器就不起作用了。原因是：如果手工增加拦截器，系统不会将默认的拦截器附加到它上面。

解决办法，用手工的方法再重新导入一次

<result name="success">/success.jsp</result>

<result name="input">/register2.jsp</result>

<interceptor-ref name="myInterceptor3"></interceptor-ref>

<interceptor-ref name="defaultStack"></interceptor-ref>

</action>

拦截器增加参数

1在定义拦截器的时候使用

Struts.xml

<param name="hello">world</param>

</interceptor>

2在使用的时候定义，同时使用时的定义会覆盖点定义时使用的变量

<result name="success">/success.jsp</result>

<result name="input">/register2.jsp</result>

<interceptor-ref name="myInterceptor">

<param name="hello">welcome</param>

</interceptor-ref>

<interceptor-ref name="defaultStack"></interceptor-ref>

结果显示welcome。

MyInterceptor拦截类

public class MyInterceptor implements Interceptor

{

//增加和name相同的名称的属性并增加GETSET方法

private String hello;

-----增加GETSET方法---------

public void destroy()

{

System.out.println("destroy");

}

public void init()

{

System.out.println("init");

System.out.println(hello);

}

public String intercept(ActionInvocation invocation) throws Exception

{

System.out.println("intercept");

String result = invocation.invoke();

System.out.println("finish");

return result;

}

自定义拦截器栈

<param name="hello">world</param>

</interceptor>

<interceptor-stack name="myStack">

<interceptor-ref name="myInterceptor"></interceptor-ref>

<interceptor-ref name="defaultStack"></interceptor-ref>

</interceptor-stack>

</interceptors>

<result name="success">/success.jsp</result>

<result name="input">/register2.jsp</result>

<interceptor-ref name="defaultStack"></interceptor-ref>

</action>

改变默认拦截器

//在包下定义默认的拦截器，会应用到说有的action中，但如果action中定义了自己的拦截器则默认拦截器就对它不起作用了：

<param name="hello">world</param>

</interceptor>

<interceptor-stack name="myStack">

<interceptor-ref name="myInterceptor"></interceptor-ref>

<interceptor-ref name="defaultStack"></interceptor-ref>

</interceptor-stack>

</interceptors>

//定义默认拦截器

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

<result name="success">/success.jsp</result>

<result name="input">/register2.jsp</result>

</action>

简化拦截器只实现主要的：

public class MyInterceptor2 extends AbstractInterceptor

{

@Override

public String intercept(ActionInvocation invocation) throws Exception

{

System.out.println("intercept2");

String result = invocation.invoke();

System.out.println("finish2");

return result;

}

拦截器的顺序和栈执行的先后有关：回来的顺序和执行的顺序相反

<interceptor-stack name="myStack">

<interceptor-ref name="myInterceptor"></interceptor-ref>

<interceptor-ref name="myInterceptor2"></interceptor-ref>

<interceptor-ref name="defaultStack"></interceptor-ref>

</interceptor-stack>

方法过滤拦截器

public class MyInterceptor3 extends MethodFilterInterceptor

{

@Override

protected String doIntercept(ActionInvocation invocation) throws Exception

{

System.out.println("my interceptor3");

String result = invocation.invoke();

return result;

}

配置包含谁和拦截谁struts.xml

</interceptor>

<interceptor-stack name="myStack">

<interceptor-ref name="defaultStack"></interceptor-ref>

</interceptor-stack>

</interceptors>

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

<result name="success">/success.jsp</result>

<result name="input">/register2.jsp</result>

<!-- 应用拦截器拦截谁不拦截谁,只要include包含的都被执行，优先级高à

<interceptor-ref name="myInterceptor3">

<param name="excludeMethods">test,execute</param>

</interceptor-ref>

<interceptor-ref name="defaultStack"></interceptor-ref>

</action>

</package>

</struts>

监听器PreResultListener接口，用于执行excuse之后，在转到JSP页面之前被调用。

建立监听器

/**

* 监听类

* @author 向先函

public class MyListener implements PreResultListener

{

//resultCode是结果如input不成功，success表示成功等

public void beforeResult(ActionInvocation invocation, String resultCode)

{

System.out.println("result : " + resultCode);

}

注册到拦截器

public class MyInterceptor3 extends MethodFilterInterceptor

{

@Override

protected String doIntercept(ActionInvocation invocation) throws Exception

{

//注册监听器，只要把实例加进去就行

invocation.addPreResultListener(new MyListener());

System.out.println("my interceptor3");

String result = invocation.invoke();

System.out.println("after my interceptor3 finished");

return result;

}

程序综合，登录提交：解决非法访问

新建拦截器：

package com.test.interceptor;

import java.util.Map;

import com.opensymphony.xwork2.Action;

import com.opensymphony.xwork2.ActionInvocation;

import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class AuthInterceptor extends AbstractInterceptor

{

@Override

@SuppressWarnings("unchecked")

public String intercept(ActionInvocation invocation) throws Exception

{

//Session 已经被放到容器里边了

Map map = invocation.getInvocationContext().getSession();

if(map.get("user") == null)

{

return Action.LOGIN;

}

else

{

return invocation.invoke();

}

配置Action.LOGIN

<global-results>

<result name="login" type="redirect">/login2.jsp</result>

</global-results>

处理LOGINaCTION类

public class LoginAction extends ActionSupport

{ @SuppressWarnings("unchecked")

public String execute() throws Exception

{

if ("hello".equals(this.getUsername().trim())

&& "world".equals(this.getPassword().trim()))

{

Map map = ActionContext.getContext().getSession();

map.put("user","valid");

return "success";

}

else

{

this.addFieldError("username", "username or password error");

return "failer";

}

注册拦截器：

</interceptor>