RESTEasy `ExceptionMapper` – 异常处理示例 - 《HowToDoInJava 中文系列教程》

1. Resteasy ExceptionMapper - 自定义异常处理器
2. Resteasy REST API
3. RESTEasy ExceptionMapper演示
- 3.1 有效请求
- 3.2 无效请求 - 引发异常

原文： https://howtodoinjava.com/resteasy/exception-handling-in-jax-rs-resteasy-with-exceptionmapper/

学习使用 resteasy ExceptionMapper接口实现创建和处理自定义异常。 ExceptionMapper是供应器的契约，该供应器将 Java 异常映射到Response对象。

必须使用@Provider注解ExceptionMapper接口的实现才能正常工作。

1. Resteasy `ExceptionMapper` - 自定义异常处理器

ExceptionMapper的示例实现供应器类如下所示：

package com.howtodoinjava.exception;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import javax.ws.rs.ext.ExceptionMapper;
import javax.ws.rs.ext.Provider;
@Provider
public class MyApplicationExceptionHandler implements ExceptionMapper<MyApplicationException> 
{
    @Override
    public Response toResponse(MyApplicationException exception) 
    {
        return Response.status(Status.BAD_REQUEST).entity(exception.getMessage()).build();    
    }
}

自定义异常类MyApplicationException.java的编写方式为：

package com.howtodoinjava.exception;
import java.io.Serializable;
public class MyApplicationException extends Exception implements Serializable
{
    private static final long serialVersionUID = 1L;
    public MyApplicationException()    {
        super();
    }
    public MyApplicationException(String msg)    {
        super(msg);
    }
    public MyApplicationException(String msg, Exception e)    {
        super(msg, e);
    }
}

2. Resteasy REST API

为了测试ExceptionMapper实现，我编写了以下 resteasy REST API。

package com.howtodoinjava.rest;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Response;
import org.jboss.resteasy.spi.validation.ValidateRequest;
import com.howtodoinjava.exception.MyApplicationException;
@Path("/rest")
public class UserService 
{
    @Path("/users/{id}")
    @GET
    @ValidateRequest
    public Response getUserBId    ( @PathParam("id") String id ) throws MyApplicationException
    {
        //validate mandatory field
        if(id == null)
        {
            throw new MyApplicationException("id is not present in request !!");
        }
        //Validate proper format
        try
        {
            Integer.parseInt(id);
        }
        catch(NumberFormatException e)
        {
            throw new MyApplicationException("id is not a number !!");
        }
        //Process the request
        return Response.ok().entity("User with ID " + id + " found !!").build();
    }
}