SEVERE: MessageBodyWriter not found for media type

问题:

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.

回答1:

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.}

回答2:

The solution may be to make ensure that the model classes have a no-argument constructor.

And add this dependency on your pom.XML:

<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-moxy</artifactId>
</dependency>

回答3:

I had the same issue, i solved it by addind a empty constructor to the class

public SandBoxClass(){} //-> solved the issue**

public SandBoxClass(Integer arg1, Integer arg2) {
        this.arg1=arg1;
        this.arg2=arg2;
}

回答4:

If you already have the jersey-media-moxy dependency added into your pom.xml. Make sure your entity class has the default constructor. I got this issue when I introduced a paramatrized constructor in the model class. Adding the default constructor again worked for me.

回答5:

1. Update Library Jax-RS 2.0 and Jersey 2.5.1(JAX-RS-RI) only
2. Return Bean object(todo) not response because while auto generating json or xml it response create issue.