严重：找不到媒体类型= application / json的MessageBodyWriter，type = class com.jersey.jaxb.Todo，genericType = class com.jersey.jaxb.Todo [英] SEVERE: MessageBodyWriter not found for media type=application/json, type=class com.jersey.jaxb.Todo, genericType=class com.jersey.jaxb.Todo

问题描述

我正在尝试创建一个RESTful网络服务，我创建了一个，但我得到了一个

找不到媒体类型的MessageBodyWriter = application / json error

我的 Todo 类：

  package com.jersey.jaxb; 
 
 import javax.xml.bind.annotation.XmlAccessType; 
 import javax.xml.bind.annotation.XmlAccessorType; 
 import javax.xml.bind.annotation.XmlElement; 
 import javax.xml.bind.annotation.XmlRootElement; 
 import javax.xml.bind.annotation.XmlType; 
 import org.pojomatic.Pojomatic; 
 import org.pojomatic.annotations.AutoProperty; 
 
 @XmlRootElement 
 @XmlType（name =todo）
 @XmlAccessorType（XmlAccessType.FIELD）
 @AutoProperty 
 public class Todo {
 
 @XmlElement（name =summary）
 private final String summary; 
 
 @XmlElement（name =description）
 private final String description; 
 
 public String getSummary（）{
 return summary; 
} 
 
 public String getDescription（）{
 return description; 
} 
 
 public Todo（）{
 this（new Builder（））; 
} 
 
 public Todo（Builder builder）{
 this.summary = builder.summary; 
 this.description = builder.description; 
} 
 
 @Override 
 public boolean equals（Object o）{
 return Pojomatic.equals（this，o）; 
} 
 
 @Override 
 public int hashCode（）{
 return Pojomatic.hashCode（this）; 
} 
 
 @Override 
 public String toString（）{
 return Pojomatic.toString（this）; 
} 
 
 public static class Builder {
 private String description; 
 private String summary; 
 
公共构建器摘要（字符串摘要）{
 this.summary = summary; 
返回此; 
} 
 
公共构建器描述（字符串描述）{
 this.description = description; 
返回此; 
} 
 
 public Todo build（）{
 return new Todo（this）; 
} 
} 
} 
  

我的资源： -

  package com.jersey.jaxb; 
 
 import javax.ws.rs.Path; 
 import javax.ws.rs.core.MediaType; 
 import javax.ws.rs.Produces; 
 import javax.ws.rs.GET; 
 
 import javax.ws.rs.core.Response; 
 import javax.ws.rs.core.Response.Status; 
 
 @Path（/ todo）
公共类TodoResource {
 
 @GET 
 @Produces（MediaType.APPLICATION_JSON）
 public响应getTodo（）{
 Todo todo = new Todo.Builder（）。description（我的Todo对象）。summary（Created）。build（）; 
返回Response.status（Status.OK）.entity（todo）.build（）; 
} 
 
} 
  

我的web.xml：

 <？xml version =1.0encoding =UTF-8？> 
< web-app xmlns：xsi =http://www.w3.org/2001/XMLSchema-instancexmlns =http://java.sun.com/xml/ns/javaeexmlns ：web =http://java.sun.com/xml/ns/javaee/web-app_2_5.xsdxsi：schemaLocation =http://java.sun.com/xml/ns/javaee http：// java.sun.com/xml/ns/javaee/web-app_2_5.xsdid =WebApp_IDversion =2.5> 
< welcome-file-list> 
< welcome-file> index.html< / welcome-file> 
< welcome-file> index.htm< / welcome-file> 
< welcome-file> index.jsp< / welcome-file> 
< welcome-file> default.html< / welcome-file> 
< welcome-file> default.htm< / welcome-file> 
< welcome-file> default.jsp< / welcome-file> 
< / welcome-file-list> 
< display-name> MyFirstWebService< / display-name> 
< servlet> 
< servlet-name> Jersey REST服务< / servlet-name> 
< servlet-class> org.glassfish.jersey.servlet.ServletContainer< / servlet-class> 
< init-param> 
< param-name> jersey.config.server.provider.packages< / param-name> 
< param-value> com.jersey.jaxb< / param-value> 
< / init-param> 
< load-on-startup> 1< / load-on-startup> 
< / servlet> 
< servlet-mapping> 
< servlet-name> Jersey REST服务< / servlet-name> 
< url-pattern> / rest / *< / url-pattern> 
< / servlet-mapping> 
 
< / web-app> 
  

我的图书馆：

  aopalliance-repackaged-2.4.0-b10.jar 
 asm-debug-all-5.0.2.jar 
 hk2-api-2.4.0-b10.jar 
 hk2-locator-2.4.0-b10.jar 
 hk2-utils-2.4.0-b10.jar 
 jackson-jaxrs-json-provider-2.2.3.jar 
 javassist- 3.18.1-GA.jar 
 javax.annotation-api-1.2.jar 
 javax.inject-2.4.0-b10.jar 
 javax.servlet-api-3.0.1.jar 
 javax.ws.rs-api-2.0.1.jar 
 jaxb-api-2.2.7.jar 
 jersey-client.jar 
 jersey-common.jar 
 jersey-container-servlet.jar 
 jersey-container-servlet-core.jar 
 jersey-guava-2.17.jar 
 jersey-media-jaxb.jar 
 jersey- server.jar 
 org.osgi.core-4.2.0.jar 
 osgi-resource-locator-1.0.1.jar 
 persistence-api-1.0.jar 
 validation- api-1.1.0.Final.jar 
  

当我在Tomcat服务器上运行此应用程序并运行：
。

 <依赖性> 
< groupId> org.glassfish.jersey.media< / groupId> 
< artifactId> jersey-media-json-jackson< / artifactId> 
< version> $ {jersey2.version}< / version> 
< / dependency> 
  

_{注意：我们不需要注册具有上述依赖关系的任何内容，都可以通过自动发现功能< /泽西岛。如果我们由于某种原因禁用自动发现，您将需要显式注册 JacksonFeature 。}

I am trying to create a RESTful web-service and I created one but I am getting a

MessageBodyWriter not found for media type=application/json error

My Todo class:

package com.jersey.jaxb;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import org.pojomatic.Pojomatic;
import org.pojomatic.annotations.AutoProperty;

@XmlRootElement
@XmlType(name = "todo")
@XmlAccessorType(XmlAccessType.FIELD)
@AutoProperty
public class Todo {

    @XmlElement(name = "summary")
    private final String summary;

    @XmlElement(name = "description")
    private final String description;

    public String getSummary() {
        return summary;
    }

    public String getDescription() {
        return description;
    }

    public Todo() {
        this(new Builder());    
    }

    public Todo(Builder builder) {
        this.summary = builder.summary;
        this.description = builder.description;
    }

    @Override
    public boolean equals(Object o) {
        return Pojomatic.equals(this, o);
    }

    @Override
    public int hashCode() {
        return Pojomatic.hashCode(this);
    }

    @Override
    public String toString() {
        return Pojomatic.toString(this);
    }

    public static class Builder {
        private String description;
        private String summary;

        public Builder summary(String summary) {
            this.summary = summary;
            return this;
        }

        public Builder description(String description) {
            this.description = description;
            return this;
        }

        public Todo build() {
            return new Todo(this);
        }
    }
}

And my Resource:-

package com.jersey.jaxb;

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

import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;

@Path("/todo")
public class TodoResource {

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response getTodo(){
        Todo todo = new Todo.Builder().description("My Todo Object").summary("Created").build();
        return Response.status(Status.OK).entity(todo).build();
    }

}

My web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<welcome-file-list>
  <welcome-file>index.html</welcome-file>
  <welcome-file>index.htm</welcome-file>
  <welcome-file>index.jsp</welcome-file>
  <welcome-file>default.html</welcome-file>
  <welcome-file>default.htm</welcome-file>
  <welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<display-name>MyFirstWebService</display-name>
<servlet>
  <servlet-name>Jersey REST Service</servlet-name>
  <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
   <init-param>
     <param-name>jersey.config.server.provider.packages</param-name>
     <param-value>com.jersey.jaxb</param-value>
   </init-param>
   <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
  <servlet-name>Jersey REST Service</servlet-name>
  <url-pattern>/rest/*</url-pattern>
</servlet-mapping>

</web-app>  

My Libraries:

aopalliance-repackaged-2.4.0-b10.jar
asm-debug-all-5.0.2.jar
hk2-api-2.4.0-b10.jar
hk2-locator-2.4.0-b10.jar
hk2-utils-2.4.0-b10.jar
jackson-jaxrs-json-provider-2.2.3.jar
javassist-3.18.1-GA.jar
javax.annotation-api-1.2.jar
javax.inject-2.4.0-b10.jar
javax.servlet-api-3.0.1.jar
javax.ws.rs-api-2.0.1.jar
jaxb-api-2.2.7.jar
jersey-client.jar
jersey-common.jar
jersey-container-servlet.jar
jersey-container-servlet-core.jar
jersey-guava-2.17.jar
jersey-media-jaxb.jar
jersey-server.jar
org.osgi.core-4.2.0.jar
osgi-resource-locator-1.0.1.jar
persistence-api-1.0.jar
validation-api-1.1.0.Final.jar

When I run this application on Tomcat server and run this : http://localhost:8080/MyFirstWebService/rest/todo

I get the error:

SEVERE: MessageBodyWriter not found for media type=application/json, type=class com.jersey.jaxb.Todo, genericType=class com.jersey.jaxb.Todo.

解决方案

You have jackson-jaxrs-json-provider which is a start..

But...

that artifact is still dependent on Jacskon itself, which includes all these artifacts

That's why we use Maven^[1] (so we don't have to worry about this kind of thing :-). So go find these.

Then just add the package to the web.xml, and it should work

<param-name>jersey.config.server.provider.packages</param-name>
<param-value>
    com.jersey.jaxb,
    com.fasterxml.jackson.jaxrs.json
</param-value>

---

_{1. Maven dependency}

<dependency>
  <groupId>com.fasterxml.jackson.jaxrs</groupId>
  <artifactId>jackson-jaxrs-json-provider</artifactId>
  <version>2.2.3</version>
</dependency>

_{Or use the below Jersey "wrapper" for the above dependency. It will register the Jackson providers (so we don't need to explicitly register like above), and the Jackson exception mappers, and start from version 2.17, provides support for Entity Data Filtering.}

<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-json-jackson</artifactId>
    <version>${jersey2.version}</version>
</dependency>

_{Note: The fact that we don't have to register anything with the above dependency, is made possible through the Auto-discovery feature of Jersey. If we for some reason disable the auto-discovery, you will want to explicitly register the JacksonFeature.}

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