MVC框架-mentawai（6）

过滤器

过滤器是mentawai框架的组件。你可以在应用的某个action中进行配置，也可以对所有action进行配置。

在应用管理器中创建

// 应用于指定action上的过滤器    @Override     public void loadActions() {          action("/Hello", HelloAction.class, "sayHi")            .filter(new SomeFilter())              .on(SUCCESS,   redir("/index.jsp"));      }  // 一个作用于所有action的全局过滤器    @Override     public void loadFilters() {          filter(new SomeGlobalFilter());      }

基本使用示例:

import org.mentawai.core.*;  import java.util.*;  public class CacheFilter implements Filter {      private static final String KEY = "cache";      @Override    public String filter(InvocationChain chain) throws Exception {          Action action = chain.getAction();          Context application = action.getApplication();          Map<String, Object> cache = (Map<String, Object>) application.getAttribute(KEY);          if (cache != null) {              Input input = action.getInput();              input.setValue(KEY, cache);          }          return chain.invoke(); // next filter or the action      }      @Override    public void destroy() { }  }  

一个简单的授权过滤器
tips：你不用编写授权过滤器，因为这是框架的特性之一

import org.mentawai.core.*;  public class AuthenticationFilter implements Filter {      public static final String LOGIN = "login";      @Override    public String filter(InvocationChain chain) throws Exception {          Action action = chain.getAction();                 Context session = action.getSession();          if (session.hasAttribute("user")) {              return chain.invoke();          }          return LOGIN;      }      @Override          public void destroy() { }  } 

在action执行之前或之后做修改

import org.mentawai.core.*;  import java.util.Date;  public class TimerFilter implements Filter {      @Override    public String filter(InvocationChain chain) throws Exception {          Action action = chain.getAction();          Output output = action.getOutput();          output.setValue("timeBefore", new Date()); // 在action执行之前         long now = System.currentTimeMillis();          String result = chain.invoke();          long totalTime = System.currentTimeMillis() - now;          output.setValue("timeAfter", new Date()); // action执行之后        output.setValue("totalTime", totalTime);          return result;      }      @Override    public void destroy() { }  }  

在action结果执行之后修改

package examples.helloworld.filter;  import org.mentawai.core.*;  import java.util.Date;  public class TimerFilter implements AfterConsequenceFilter {      @Override     public String filter(InvocationChain chain) throws Exception {          Action action = chain.getAction();          Output output = action.getOutput();          output.setValue("timeBefore", new Date().toString()); // before the action execution...          long now = System.currentTimeMillis();          String result = chain.invoke();          long totalTime = System.currentTimeMillis() - now;          output.setValue("timeAfter", new Date().toString()); // after the action execution...          output.setValue("totalTime", totalTime);          // save the initial time for the consequence here...          Input input = action.getInput();          input.setValue("initialTime", System.currentTimeMillis());          return result;      }      @Override    public void afterConsequence(Action action, Consequence c, boolean conseqExecuted, boolean actionExecuted, String result) {          // Note: You should understand that after the consequence is executed it is too        // late to include anything in the response to the client.        if (!conseqExecuted) {              System.out.println("There was an error executing the consequence!");          } else {              Input input = action.getInput();              Long initialTime = (Long) input.getValue("initialTime");              long totalTime = System.currentTimeMillis() - initialTime.longValue();              System.out.println("The total time for the consequence was: " + totalTime);          }      }      @Override     public void destroy() { }  }