在Tapestry中使用redirect-after-post模式控制表单提交

Tapestry中表单的提交有很多问题，刷新导致表单的重复提交、臭名昭著的dirty form warning、
显示不友好的URL等，这些都可以使用redirect-after-post模式来避免，也就是post表单之后将页面redirect一下，
这样地址栏显示的就是redirect之后的页面，刷新的也将是这个页面，而且redirect之后的页面一般为Page页面，
可以使用friendlyUrl来显示友好的url。

要使用这个模式，不得不提到一个ILink接口，T4中可接受的listener方法中一个方法签名是这样的:

public ILink listenerMethod(Parameter parameter);  

这个方法的返回值为ILink，如果T4侦测到是这个返回值的话，将自动redirect到ILink指定的页面。
而且ILink可以为纯页面的Link也可以是带有参数的Link。纯页面Link也就是page service生成的link，
带参数的link为external service生成的link，具体link的生成代码如下：  

   @InjectObject("engine-service:page")  
    public abstract IEngineService getPageService();  
      
    public ILink getPageLink(String pageName) {  
      
               return getPageService().getLink(false, pageName);       
      }  
        
     @InjectObject("engine-service:external")  
     public abstract IEngineService getExternalService();  
 
     public ILink getExternalLink(String pageName, Object[] parameters) {  
     
        ExternalServiceParameter esp = new ExternalServiceParameter(pageName,  
     
               parameters);  
     
        return getExternalService().getLink(false, esp);  
     
     }    

将上述方法放入到你的项目中自定义的MyBasePage（继承Tapestry的BasePage）中，然后让你的

页面类继承MyBasePage，这样就可以使用上述方法了。

这样在页面提交时可以如下调用

    public ILink onDelete(Long id){  
                
    //your code to delete object  
          
    return getPageLink(getPageName());//删除后重新redirect到本页面  
     
   }  
     
    当然如果这个页面带参数，例如catgoryId=1，则代码如下：  
     
    public ILink onDelete(Long id){  
         
   //your code to delete object  
       
    return getExternalLink(getPageName(),new Object[]{categoryId});  
    //删除后重新redirect到本页面,并带一个参数  
     
   }  

上述方式通过继承来实现方法调用，感觉不是很好，我们可以利用Tapestry的易扩展特性来扩展它，
首先想到的就是注释方式来注入，例如我想实现如下注入

    @InjectPageLink（“Home“）      
    Public abstract ILink getHomeLink();  
        
    @InjectExternalLink（“Category“）   
    Public abstract ILink getCategoryLink(Long categoryId);  

这样即去掉了页面的继承，也显得比较直接。

首先是定义注释类

   import java.lang.annotation.ElementType;       
    import java.lang.annotation.Retention;   
    import java.lang.annotation.RetentionPolicy;   
    import java.lang.annotation.Target;  
         
    @Target( { ElementType.METHOD })      
    @Retention(RetentionPolicy.RUNTIME)      
    public @interface InjectPageLink {     
      String value();   
    }  

然后写注释的worker类

     import java.lang.reflect.Method;  
   import java.lang.reflect.Modifier;     
   import org.apache.hivemind.ApplicationRuntimeException;     
   import org.apache.hivemind.Location;  
   import org.apache.hivemind.service.BodyBuilder;   
   import org.apache.hivemind.service.MethodSignature;   
   import org.apache.tapestry.annotations.AnnotationUtils;  
   import org.apache.tapestry.annotations.MethodAnnotationEnhancementWorker;    
   import org.apache.tapestry.engine.ILink;      
   import org.apache.tapestry.enhance.EnhancementOperation;      
   import org.apache.tapestry.spec.IComponentSpecification;  
    
   public class InjectPageLinkAnnotationWorker implements   
          MethodAnnotationEnhancementWorker {  
 
       public void performEnhancement(EnhancementOperation op,  
     
              IComponentSpecification spec, Method method, Location location) {  
     
          if (!method.getReturnType().equals(ILink.class))  
     
              throw new ApplicationRuntimeException(  
     
                     "InjectPage annotation must return ILink");  
    
          InjectPageLink injectPageLink = method.getAnnotation(InjectPageLink.class);  
          String pageName = injectPageLink.value();  
          BodyBuilder builder = new BodyBuilder();  
          builder.begin();       
          builder.addln("return getPage().getRequestCycle().getInfrastructure().getServiceMap().getService( 
                          org.apache.tapestry.Tapestry.PAGE_SERVICE).getLink(false,\"{0}\");", pageName);  
          builder.end();  
          op.addMethod(Modifier.PUBLIC, new MethodSignature(method), builder  
                 .toString(), location);  

          if (isGetter(method))  
              op.claimReadonlyProperty(AnnotationUtils.getPropertyName(method));      
       }  
   
       boolean isGetter(Method method) {  
     
          return method.getName().startsWith("get")  
                 && method.getParameterTypes().length == 0;    
       }     
   }   

External的同样两个类

 import java.lang.annotation.ElementType;       
    import java.lang.annotation.Retention;  
    import java.lang.annotation.RetentionPolicy;      
    import java.lang.annotation.Target;  
    
    @Target( { ElementType.METHOD })    
    @Retention(RetentionPolicy.RUNTIME)     
    public @interface InjectExternalLink {      
       String value();      
    }  

Work类

 import java.lang.reflect.Method;    
 import java.lang.reflect.Modifier;    
 import org.apache.hivemind.ApplicationRuntimeException;   
 import org.apache.hivemind.Location;  
 import org.apache.hivemind.service.BodyBuilder;  
 import org.apache.hivemind.service.MethodSignature;  
 import org.apache.tapestry.Tapestry;  
 import org.apache.tapestry.annotations.AnnotationUtils;  
 import org.apache.tapestry.annotations.MethodAnnotationEnhancementWorker;  
 import org.apache.tapestry.engine.ILink;   
 import org.apache.tapestry.enhance.EnhancementOperation;  
 import org.apache.tapestry.spec.IComponentSpecification;  
    
 public class InjectExternalLinkAnnotationWorker implements  
           MethodAnnotationEnhancementWorker {  

     public void performEnhancement(EnhancementOperation op,  
            IComponentSpecification spec, Method method, Location location) {  
   
        if (!method.getReturnType().equals(ILink.class))  
            throw new ApplicationRuntimeException(  
                   "injectExternalLink annotation must return ILink");  
        InjectExternalLink injectExternalLink = method  
               .getAnnotation(InjectExternalLink.class);  
        String pageName = injectExternalLink.value();   
        BodyBuilder builder = new BodyBuilder();   
        builder.begin();    
        Class[] parameterTypes = method.getParameterTypes();     
        int paramCount = Tapestry.size(parameterTypes);   
        if (paramCount > 0) {     
            if (parameterTypes[0].isArray()) {     
               builder.addln(    
                             "return getPage().getRequestCycle().getInfrastructure().getServiceMap(). 
						getService(org.apache.tapestry.Tapestry.EXTERNAL_SERVICE).getLink(false, new org.apache.tapestry.engine.ExternalServiceParameter(\"{0}\",$1));",    
                             pageName);    
			} else {   
               builder    
                      .addln(     
                             "java.lang.Object[] params = new java.lang.Object[{0}];",    
                             paramCount);     
               for (int i = 0; i < paramCount; i++) {    
                   builder.add("params[{0}] = ", i);  
                   if (parameterTypes[i].isPrimitive())    
                      builder.add("($w) ");      
                   // Parameter $0 is this, so $1 is the first real parameter.    
                   builder.addln("${0};", i + 1);     
               }    
               builder     
                      .addln(     
                             "return getPage().getRequestCycle().getInfrastructure().getServiceMap().getService(org.apache.tapestry.Tapestry.EXTERNAL_SERVICE).getLink(false, new org.apache.tapestry.engine.ExternalServiceParameter(\"{0}\",params));",    
                             pageName);     
            }     
        }    
        builder.end();  
        op.addMethod(Modifier.PUBLIC, new MethodSignature(method), builder    
               .toString(), location);  
        if (isGetter(method))     
            op.claimReadonlyProperty(AnnotationUtils.getPropertyName(method));    
     }    
     boolean isGetter(Method method) {   
     // We already know the return type is String    
        return method.getName().startsWith("get")     
               && method.getParameterTypes().length == 0;    
     }    
 }  
 

类写好了，然后就是贡献到Tapestry中

<module id="your.model.annotation" version="1.0.0" package="your.package.annotations">       
		<contribution configuration-id="tapestry.annotation.MethodWorkers">       
			<worker annotation="InjectPageLink" object="instance:InjectPageLinkAnnotationWorker"/>       
			<worker annotation="InjectExternalLink" object="instance:InjectExternalLinkAnnotationWorker"/>      
		<contribution>     
  <module>  

好了将你的module放入项目hivemodule.Xml作为子module。

http://www.iteye.com/post/178572