Struts2 拦截器总结（内置和新建）[转]
?? 拦截器的类已经定义在特殊的配置文件中，这个配置文件的名字就叫做struts-default.xml,如果你继承了struts-default默认的包名，那你就可以使用这些拦截器了，否则你必须在你自己的包中定义拦截器在<interceptors>中进行定义。
下面是Struts2中的内置拦截器介绍
InterceptorNameDescription
Alias Interceptoralias在不同的请求之间将参数在不同的名字间转换，请求内容不变.
Chaining Interceptorchain让前面一个Action的属性可以被后一个Action访问
Checkbox InterceptorcheckboxAdds automatic checkbox handling code that detect an unchecked checkbox and add it as a parameter with a default (usually 'false') value. Uses a specially named hidden field to detect unsubmitted checkboxes. The default unchecked value is overridable for non-boolean value'd checkboxes.
Cookie Interceptorcookie使用配置的name、value来设置cookies
Conversion Error InterceptorconversionError将错误从ActionContext中添加到Action的属性字段中
Create Session InterceptorcreateSession自动地创建HttpSession，用来为需要使用到HttpSession的拦截器服务
DebuggingInterceptordebugging提供不同的调试用的页面来展示内部的数据状况
Execute and Wait InterceptorexecAndWait在后台执行Action，同时将用户带到一个中间的等待页面
Exception Interceptorexception将异常定位到一个页面
File Upload InterceptorfileUpload提供文件上传功能
I18n Interceptori18n记录用户选择的locale
Logger Interceptorlogger输出Action的名字
Message Store Interceptorstore存储或者访问实现ValidationAware接口的Action类出现的消息、错误、字段错误等。
Model Driven Interceptormodel-driven如果一个类实现了ModelDriven，将getModel得到的结果放在ValueStack中
Scoped Model Driven Interceptorscoped-model-driven如果一个Action实现了ScopedModelDriven，则这个拦截器会从相应的Scope中取出model，调用Action的setModel方法将其放入Action内部
Parameters Interceptorparams将请求中的参数设置到Action中去
Prepare Interceptorprepare如果Action实现了Preparable，则该拦截器调用Action类的prepare方法
Scope Interceptorscope将Action状态存入Session和Application的简单方法
Servlet Config InterceptorservletConfig提供访问HttpServletRequest和HttpServletResponse的方法，以Map的方式访问
Static Parameters InterceptorstaticParams从struts.xml文件中将<action>中的<param>下的内容设置到对应的Action中
Roles Interceptorroles确定用户是否具有JAAS指定的Role，否则不予执行
Timer Interceptortimer输出Action执行的时间
Token Interceptortoken通过Token来避免双击
Token Session InterceptortokenSession和Token Interceptory一样，不过双击的时候把请求的数据存储在Session中
Validation Interceptorvalidation使用action-validation.xml文件中定义的内容校验提交的数据
Workflow Interceptorworkflow调用Action的validate的方法，一旦有错返回，重新定位到INPUT页面
Parameter Filter InterceptorN/A从参数列表中删除不必要的参数
Profiling Interceptorprofiling通过参数激活profile
? 每一个拦截器都可以配置参数，有两种方式配置参数，一是针对每一个拦截器定义参数，二是针对一个拦截器堆栈统一定义所有的参数，例如：
<interceptor-ref name="validation"> <param name="excludeMethods">myValidationExcudeMethod</param> </interceptor-ref> <interceptor-ref name="workflow"> <param name="excludeMethods">myWorkflowExcludeMethod</param> </interceptor-ref>
或者
<interceptor-ref name="defaultStack"> <param name="validation.excludeMethods">myValidationExcludeMethod</param> <param name="workflow.excludeMethods">myWorkflowExcludeMethod</param> </interceptor-ref>
每一个拦截器都有两个默认的参数：
excludeMethods - 过滤掉不使用拦截器的方法和
includeMethods – 使用拦截器的方法。
需要说明的几点：
1 拦截器执行的顺序按照定义的顺序执行，例如：
<interceptor-stack name="xaStack"> <interceptor-ref name="thisWillRunFirstInterceptor"/> <interceptor-ref name="thisWillRunNextInterceptor"/> <interceptor-ref name="followedByThisInterceptor"/> <interceptor-ref name="thisWillRunLastInterceptor"/> </interceptor-stack>
的执行顺序为：
thisWillRunFirstInterceptor thisWillRunNextInterceptor followedByThisInterceptor thisWillRunLastInterceptor MyAction1 MyAction2 (chain) MyPreResultListener MyResult (result) thisWillRunLastInterceptor followedByThisInterceptor thisWillRunNextInterceptor thisWillRunFirstInterceptor
2 使用默认拦截器配置每个Action都需要的拦截器堆栈，例如：
<action name="login" ROLE " );
???????? if ( null != role) {
??????????? Object o = ai.getAction();
???????????? if (o instanceof RoleAware) {
??????????????? RoleAware action = (RoleAware) o;
??????????????? action.setRole(role);
??????????? }
???????????? return ai.invoke();
??????? } else {
???????????? return Action.LOGIN;
??????? }???????
??? }
}
?
?? 以上代码相当简单，我们通过检查session是否存在键为“ROLE”的字符串，判断用户是否登陆。如果用户已经登陆，将角色放到Action中，调用Action；否则，拦截直接返回Action.LOGIN字段。为了方便将角色放入Action，我定义了接口tutorial.RoleAware，代码如下：
package tutorial;
public interface RoleAware {
???? void setRole(String role);
}
?? 接着，创建Action类tutorial.AuthorizatedAccess模拟访问受限资源，它作用就是通过实现RoleAware获取角色，并将其显示到ShowUser.jsp中，代码如下：
package tutorial;
import com.opensymphony.xwork2.ActionSupport;
public class AuthorizatedAccess extends ActionSupport implements RoleAware {
???? private String role;
???
???? public void setRole(String role) {
???????? this .role = role;
??? }
???
???? public String getRole() {
???????? return role;
??? }
??? @Override
???? public String execute() {
???????? return SUCCESS;
??? }
}
?? 以下是ShowUser.jsp的代码：
<% @ page? contentType = " text/html; charset=UTF-8 " %>
<% @taglib prefix = " s " uri = " /struts-tags " %>
< html >
< head >
??? < title > Authorizated User </ title >
</ head >
< body >
??? < h1 > Your role is: < s:property value ="role" /></ h1 >
</ body >
</ html >
??? 然后，创建tutorial.Roles初始化角色列表，代码如下：
package tutorial;
import java.util.Hashtable;
import java.util.Map;
public class Roles {
???? public Map < String, String > getRoles() {
??????? Map < String, String > roles = new Hashtable < String, String > ( 2 );
??????? roles.put( " EMPLOYEE " , " Employee " );
??????? roles.put( " MANAGER " , " Manager " );
???????? return roles;
??? }
}
???? 接下来，新建Login.jsp实例化tutorial.Roles，并将其roles属性赋予<s:radio>标志，代码如下：
<% @ page? contentType = " text/html; charset=UTF-8 " %>
<% @taglib prefix = " s " uri = " /struts-tags " %>
< html >
< head >
??? < title > Login </ title >
</ head >
< body >
??? < h1 > Login </ h1 >
??? Please select a role below:
??? < s:bean id ="roles" name ="tutorial.Roles" />
??? < s:form action ="Login" >
??????? < s:radio list ="#roles.roles" value ="'EMPLOYEE'" name ="role" label ="Role" />
??????? < s:submit />
??? </ s:form >
</ body >
</ html >
??? 创建Action类tutorial.Login将role放到session中，并转到Action类tutorial.AuthorizatedAccess，代码如下：
package tutorial;
import java.util.Map;
import org.apache.struts2.interceptor.SessionAware;
import com.opensymphony.xwork2.ActionSupport;
public class Login extends ActionSupport implements SessionAware {
???? private String role;???
???? private Map session;
???? public String getRole() {
???????? return role;
??? }
???? public void setRole(String role) {
???????? this .role = role;
??? }
???
???? public void setSession(Map session) {
???????? this .session = session;
??? }
??? @Override
???? public String execute() {
??????? session.put( " ROLE " , role);
???????? return SUCCESS;
??? }???
}
??
??? 最后，配置struts.xml文件，内容如下：
<! DOCTYPE struts PUBLIC
??????? "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
??????? "http://struts.apache.org/dtds/struts-2.0.dtd" >
< struts >
??? < include file ="struts-default.xml" />???
??? < package name ="InterceptorDemo" extends ="struts-default" >
??????? < interceptors >
??????????? < interceptor name ="auth" class ="tutorial.AuthorizationInterceptor" />
??????? </ interceptors >
??????? < action name ="Timer" class ="tutorial.TimerInterceptorAction" >
??????????? < interceptor-ref name ="timer" />
??????????? < result > /Timer.jsp </ result >
??????? </ action >
??????? < action name ="Login" class ="tutorial.Login" >
??????????? < result type ="chain" > AuthorizatedAccess </ result >
??????? </ action >
??????? < action name ="AuthorizatedAccess" class ="tutorial.AuthorizatedAccess" >
??????????? < interceptor-ref name ="auth" />
??????????? < result name ="login" > /Login.jsp </ result >
??????????? < result name ="success" > /ShowRole.jsp </ result >
??????? </ action >
??? </ package >
</ struts >
