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

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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:

   
   
   
   

    
    
    
    java 代码
   
   
   
   
   
   
   
   
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：   

java 代码

@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

java 代码

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

java 代码

@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

java 代码

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

   
   
   
   

    
    
    
    java 代码
   
   
   
   
   
   
   
   
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

java 代码

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

  
  
  
  

   
   
   
   java 代码
  
  
  
  
  
  
  
  
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

xml 代码

<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。

Ok ， enjoy it ！