Struts2的拦截器(interceptor)

作用：当请求进入struts2框架后，想对请求进行拦截操作(功能增强、权限控制)，需要拦截器组件

1、struts2内置拦截器

1.1 struts-default.xml中配置好的拦截器

            struts2框架已经定义好并使用的拦截器
           发送请求 -----> interceptor1---->interceptor2 -----> DemoAction

           在struts-default.xml文件中已经声明了多个拦截器

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
	"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
	"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
    <package name="test" namespace="/" extends="struts-default">
        <interceptors>
            ... ...
            <!--声明拦截器-->
            <interceptor name="modelDriven"  class="com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor"/>
            ... ...
                
            <!--声明拦截器栈-->
            <interceptor-stack name="basicStack">
                ... ...
                <interceptor-ref name="exception"/>
                ... ...
            </interceptor-stack> 
        </interceptors>
            <!-- 默认的拦截器引用 -->
            <default-interceptor-ref name="defaultStack"/>
    </package>
</struts>

1.2 源码分析interceptor的执行过程

            --->StrutsPrepareAndExecuteFilter
           --->public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
           --->execute.executeAction(request, response, mapping);
           --->dispatcher.serviceAction(request, response, mapping);
           --->ActionProxy proxy = createActionProxy();
           --->proxy.execute();
           --->retCode = invocation.invoke();
           --->
               Iterator<InterceptorMapping> interceptors;

               //判断迭代器集合中是否还有下一个
               if (interceptors.hasNext()) {
                   final InterceptorMapping interceptor = interceptors.next(); //获得当前InterceptorMapping对象
                   resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
                                   获得拦截器对象本身       调用该拦截器内部的拦截方法intercept

               } else {
                   resultCode = invokeActionOnly(); //仅仅执行当前要访问目标Action
               }

               PS：
                   resultCode：逻辑视图名，字符串

                   总结：
                       如果在interceptor中调用invocation.invoke(); 代表放行
                       如果在interceptor中return 字符串，代表不放行，且return的字符串就是要匹配的逻辑视图

               PS:
                   <interceptor name="modelDriven" class="com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor"/>
                   class InterceptorMapping{
                       private String name; //modelDriven
                       private Interceptor interceptor; //class对应全限定名的对象
                   }

2、struts2自定义拦截器

开发步骤：

1、自定义拦截器类实现interceptor接口(继承interceptor的实现类)
2、实现intercept方法，该方法封装拦截功能的逻辑代码

public class MyInterceptor1 implements Interceptor {
	@Override
	public String intercept(ActionInvocation invocation) throws Exception {
		System.out.println("MyInterceptor1执行...");
		return invocation.invoke();
	}
	
	@Override
	public void destroy() {}

	@Override
	public void init() {}
}


public class MyInterceptor2 extends AbstractInterceptor {
	@Override
	public String intercept(ActionInvocation invocation) throws Exception {
		System.out.println("MyInterceptor2执行................");
		return invocation.invoke();
	}
}

public class MyInterceptor3 extends MethodFilterInterceptor {
	@Override
	protected String doIntercept(ActionInvocation invocation) throws Exception {
		System.out.println("MyInterceptor33333执行.........");
		return invocation.invoke();
	}
}

3、在struts.xml中配置拦截器

声明拦截器
使用拦截器

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
	"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
	"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>

	<constant name="struts.devMode" value="true"></constant>
	
	<package name="test" namespace="/" extends="struts-default">
	
		<interceptors>
			<interceptor name="my2" class="com.itheima.action.interceptor.MyInterceptor2"></interceptor>
			<interceptor name="my1" class="com.itheima.action.interceptor.MyInterceptor1"></interceptor>
			<interceptor name="my3" class="com.itheima.action.interceptor.MyInterceptor3"></interceptor>
			<interceptor-stack name="my">
				<interceptor-ref name="defaultStack"></interceptor-ref>
				<interceptor-ref name="my1"></interceptor-ref>
				<interceptor-ref name="my2"></interceptor-ref>
				<interceptor-ref name="my3">
					<param name="excludeMethods">xxx</param>
				</interceptor-ref>
			</interceptor-stack>
		</interceptors>
		
		<!-- 
			细节点：拦截器的作用范围
			1、当前包下所有的Action都执行配置的拦截器
				<default-interceptor-ref name="my"></default-interceptor-ref>
			2、action可以执行自己局部的interceptor
				<action name="target_*" class="com.itheima.action.TargetAction" method="{1}">
					<interceptor-ref name="my"></interceptor-ref>
					<result name="success">/success.jsp</result>
				</action>
				
			3、action中的方法可以执行局部的interceptor
				例如：访问target的show方法执行my拦截器  访问target的xxx方法不执行my拦截器
				
				class MyInterceptor3 extends MethodFilterInterceptor 
				
				<interceptor-ref name="my3">
					<param name="excludeMethods">xxx</param>
				</interceptor-ref>
				
		 -->

		<action name="target_*" class="com.itheima.action.TargetAction" method="{1}">
			<interceptor-ref name="my"></interceptor-ref>
			<result name="success">/success.jsp</result>
		</action>
		
		<action name="target2_*" class="com.itheima.action.TargetAction2" method="{1}">
			<result name="success">/success.jsp</result>
		</action>
		
	</package>

</struts>

4、测试（访问action）

public class TargetAction extends ActionSupport {
	private String name;
	public void setName(String name) {
		this.name = name;
	}

	public String show(){
		System.out.println(name);
		return SUCCESS;
	}
	
	public String xxx(){
		return SUCCESS;
	}
}

public class TargetAction2 extends ActionSupport {
	public String show(){
		return SUCCESS;
	}
}

Struts2框架之拦截器