但是，将try-catch-finally块放在所有代码中并不是一个好习惯。 我们应该以这样一种方式设计/编码，如果发生任何不可恢复的错误，那么代码应该抛出该异常，并且应该有一个异常处理程序来捕获这些异常并提取错误详细信息，并对所有错误给出正确的错误响应错误详细信息。
RESTEasy提供了这样的ExceptionHandler机制，该机制简化了ExceptionHandling过程。
在这一部分中，我将向您展示如何使用RESTEasy的ExceptionHandlers处理异常。
步骤＃1：创建应用程序特定的异常。
*** ResourceNotFoundException.java*package com.sivalabs.resteasydemo;public class ResourceNotFoundException extends RuntimeException{private static final long serialVersionUID = 1L;public ResourceNotFoundException(String msg){super(msg);}}*** ApplicationException.java*package com.sivalabs.resteasydemo;import java.io.PrintWriter;import java.io.StringWriter;public class ApplicationException extends RuntimeException{private static final long serialVersionUID = 1L;public ApplicationException(){super();}public ApplicationException(String message, Throwable cause){super(message, cause);}public ApplicationException(Throwable cause){super(cause);}public ApplicationException(String msg){super(msg);}public String getInternalErrorMessage(){Throwable cause = this.getCause();if(cause != null){StringWriter sw = new StringWriter();PrintWriter pw = new PrintWriter(sw);cause.printStackTrace(pw);return sw.toString();}return null;}}步骤2：通过实现ExceptionMapper接口创建ExceptionHandlers。
*** ResourceNotFoundExceptionHandler.java*package com.sivalabs.resteasydemo;import javax.ws.rs.core.Response;import javax.ws.rs.ext.ExceptionMapper;import javax.ws.rs.ext.Provider;import org.springframework.stereotype.Component;@Provider@Componentpublic class ResourceNotFoundExceptionHandler implements ExceptionMapper<ResourceNotFoundException>{@Overridepublic Response toResponse(ResourceNotFoundException ex)For simplicity I am preparing error xml by hand.Ideally we should create an ErrorResponse class to hold the error info.String msg = ex.getMessage();StringBuilder response = new StringBuilder('<response>');response.append('<status>failed<status>');response.append('<message>'+msg+'<message>');response.append('<response>');return Response.serverError().entity(response.toString()).build();}}*** ApplicationExceptionHandler.java*package com.sivalabs.resteasydemo;import javax.ws.rs.core.Response;import javax.ws.rs.ext.ExceptionMapper;import javax.ws.rs.ext.Provider;import org.springframework.stereotype.Component;@Provider@Componentpublic class ApplicationExceptionHandler implements ExceptionMapper<ApplicationException>{@Overridepublic Response toResponse(ApplicationException ex){For simplicity I am preparing error xml by hand.Ideally we should create an ErrorResponse class to hold the error info.String msg = ex.getMessage();String internalError = ex.getInternalErrorMessage();StringBuilder response = new StringBuilder('<response>');response.append('<status>failed<status>');response.append('<message>'+msg+'<message>');response.append('<internalError>'+internalError+'<internalError>');response.append('<response>');return Response.serverError().entity(response.toString()).build();}}步骤＃3：更新UserResource.getUserXMLById（）方法以验证用户输入并引发相应的异常 。
@Path('{id}')@GETpublic Response getUserXMLById(@PathParam('id') Integer id) {if(id==null || id < 1 ){throw new ApplicationException('User Id['+id+'] should not be less than 1.');}User user = userService.getById(id);if(user==null ){throw new ResourceNotFoundException('No User found with Id :['+id+']');}return Response.ok(user).build();}步骤4：通过发出以下请求，测试UserResource.getUserXMLById（）服务方法。
case 1 : GET http:localhost:8080resteasy-demorestusers0Response :<response><status>failed<status><message>User Id[0] should not be less than 1.<message><internalError>null<internalError><response>case 2: GET http:localhost:8080resteasy-demorestusers100Response :<response><status>failed<status><message>No User found with Id :[100]<message><response>重要注意事项：
在Spring创建必要的对象时，我们应该让Spring知道@Provider类，以使它们在RESTEasy中注册。 我们可以通过两种方式做到这一点。
a）使用@Component注释提供程序类
b）使用组件扫描的包含过滤器。
<context：component-scan base-package ='com.sivalabs.springdemo'>
<context：include-filter expression ='javax.ws.rs.ext.Provider'type ='annotation'/> </ context：component-scan>
RESTEasy教程系列
RESTEasy教程第1部分：基础
RESTEasy教程第2部分：Spring集成
RESTEasy教程第3部分–异常处理
参考： RESTEasy教程第3部分–来自我们的JCG合作伙伴 Siva Reddy的“ 异常处理” ，位于“ 技术上的我的实验”博客上。
翻译自: https://www.javacodegeeks.com/2012/06/resteasy-tutorial-part-3-exception.html
