Raj Hassani Raj Hassani - 4 months ago 64
Java Question

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

I am trying to create a Restful web-service by surfing around the net 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.

Answer

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

But...

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

enter image description here

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.