自定义Tapestry标注

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

1. @InjectPageLink（“Home“）  //自定义
2. Public abstract ILink getHomeLink(); 
   
3. 
   
4. @InjectExternalLink（“Category“）  //自定义
5. 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) {  
   
//如果返回类型不是是ILink
        if (!method.getReturnType().equals(ILink.class))  
   
            throw new ApplicationRuntimeException(  
                   "InjectPage annotation must return ILink");  
   
        InjectPageLink injectPageLink = method.getAnnotation(InjectPageLink.class);  
   
//获得标签内赋的值
        String pageName = injectPageLink.value();  


//*********************************************************************************************************
        BodyBuilder builder = new BodyBuilder();  
  
        builder.begin();  
   
//添加抽象方法的内容
        builder .addln(  "return getPage().getRequestCycle().getInfrastructure().getServiceMap().getService( 
 org.apache.tapestry.Tapestry.PAGE_SERVICE).getLink(false,/"{0}/");",  pageName);  
 
        builder.end();  
//*********************************************************************************************************
//将生成的内容添加到抽象方法中去
        op.addMethod(Modifier.PUBLIC, new MethodSignature(method), builder .toString(), location);  

//判断是不是Getter方法
        if (isGetter(method))  
            op.claimReadonlyProperty(AnnotationUtils.getPropertyName(method));  
   
     }  
   
     boolean isGetter(Method method) {  
        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>