RestWeb服务不返回XML响应，甚至在eclipse中没有登录控制台

Question

创建restful应用程序，但它不会以XML格式返回响应。即使在点击URL时控制台上也没有日志“http://localhost:8080/message/webapi/messages".

我返回一个列表，并使用@products（MediaType.APPLICATION\uxml）以XML形式返回响应。

消息资源。Java语言

package org.porwal.restful.message.resources;

import java.util.List;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import org.porwal.restful.message.model.Message;
import org.porwal.restful.message.service.MessageService;

@Path("/messages")
public class MessageResource {

    MessageService ms = new MessageService();

    @GET
    @Produces(MediaType.APPLICATION_XML)
    public List<Message> getMessage(){
        return ms.getAllMessage();
    }

}

Message.java

package org.porwal.restful.message.model;

import java.util.Date;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement( name = "Message" )
public class Message {

    public long id;
    public String message;
    public Date created;
    public String author;

    public Message() {

    }

    public Message(long id, String message, String author) {
        this.id = id;
        this.message = message;
        this.author = author;
        this.created = new Date();
    }

    public long getId() {
        return id;
    }
    @XmlElement (name = "ID")
    public void setId(long id) {
        this.id = id;
    }
    public String getMessage() {
        return message;
    }
    @XmlElement (name = "Message")
    public void setMessage(String message) {
        this.message = message;
    }
    public Date getCreated() {
        return created;
    }
    @XmlElement (name = "Created")
    public void setCreated(Date created) {
        this.created = created;
    }
    public String getAuthor() {
        return author;
    }
    @XmlElement (name = "Author")
    public void setAuthor(String author) {
        this.author = author;
    }

}

如果我不使用@XMLRootElement注释，并且TEXT_PLAIN可以通过URL很好地返回，那么这是可行的。我还尝试删除每个字段的@xmlement，但没有成功。当我删除@XMLRootElement时，可以在eclipse控制台上的日志中看到MessageBodyWriter错误，但当包含@XMLRootElement时，则在eclipse控制台和URL上没有日志。”http://localhost:8080/message/webapi/messages“抛出错误：

缺少@XmlRootElement的情况下出错。

org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor aroundWriteTo SEVERE: MessageBodyWriter not found for media type=application/xml, type=class java.util.ArrayList, genericType=java.util.List<org.porwal.restful.message.model.Message>. This exception comes only when i commented the line "//@XmlRootElement( name = "Message" )".

HTTP状态500-内部服务器错误

有人能告诉我我错过了什么吗？

Answer 1

您需要将消息中的所有字段设置为私有。如果您将它们保留为公共的，那么JAXB将把它视为一个属性，并将其视为重复属性，因为您还有JavaBean属性（getter/setter）。

@XmlRootElement( name = "Message" )
public class Message {

    private long id;
    private String message;
    private Date created;
    private String author;

    // ...
}

我是如何通过使用通用的ExceptionMapper来解决这个问题的

@Provider
public class DebugExceptionMapper implements ExceptionMapper<Exception> {

    @Override
    public Response toResponse(Exception exception) {
        exception.printStackTrace();
        return Response.serverError().entity(exception.getMessage()).build();
    } 
}

您可以在应用程序中注册它，它将捕获未映射的异常，您可以用它做任何事情。这里我们只打印堆栈跟踪。如果我们不处理它，它就会被吞没，我们永远不会知道发生了什么。

使用ExceptionMapper运行应用程序时，我收到了一条错误消息。

Caused by: com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 4 counts of IllegalAnnotationExceptions
Class has two properties of the same name "author"
    this problem is related to the following location:
        at public java.lang.String com.example.Message.getAuthor()
        at com.example.Message
    this problem is related to the following location:
        at public java.lang.String com.example.Message.author
        at com.example.Message
Class has two properties of the same name "created"
    this problem is related to the following location:
        at public java.util.Date com.example.Message.getCreated()
        at com.example.Message
    this problem is related to the following location:
        at public java.util.Date com.example.Message.created
        at com.example.Message
Class has two properties of the same name "id"
    this problem is related to the following location:
        at public long com.example.Message.getId()
        at com.example.Message
    this problem is related to the following location:
        at public long com.example.Message.id
        at com.example.Message
Class has two properties of the same name "message"
    this problem is related to the following location:
        at public java.lang.String com.example.Message.getMessage()
        at com.example.Message
    this problem is related to the following location:
        at public java.lang.String com.example.Message.message
        at com.example.Message

你可以清楚地看到问题所在。除了避免这个错误之外，这就是封装的工作原理；字段应该是私有的，并通过getter和setter公开。