我设置了一个eclipse WebApp项目,并将Jersey和Jackson JAR放在WEB-INF / lib目录中.我想使用JSON序列化,但没有设法修复此错误：
MessageBodyWriter not found for media type=application/json, type=class com.rest.Greeting, genericType=class com.rest.Greeting. I already googled much but all the solutions are updated or don't solve my issue. Here is the structure of my project:
WEB-INF / lib文件夹包含以下JAR：
aopalliance-repackaged-2.3.0-b10.jar
asm-debug-all-5.0.2.jar
cglib-2.2.2.jar
datafactory-0.8.jar
hk2-api-2.3.0-b10.jar
hk2-locator-2.3.0-b10.jar
hk2-utils-2.3.0-b10.jar
jackson-annotations-2.4.0.jar
jackson-core-2.4.0.jar
jackson-databind-2.4.0.jar
jackson-jaxrs-base-2.4.0.jar
jackson-jaxrs-json-provider-2.4.0.jar
jackson-module-jaxb-annotations-2.4.0.jar
javassist-3.18.1-GA.jar
javax.annotation-api-1.2.jar
javax.inject-2.3.0-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-core.jar
jersey-container-servlet.jar
jersey-guava-2.13.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
web.xml中：
<?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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Rest Test</display-name>
<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>
<servlet>
<servlet-name>Greeting</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.rest</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Greeting</servlet-name>
<url-pattern>/greet/*</url-pattern>
</servlet-mapping>
</web-app>
Greeting.java：
@XmlRootElement
@Path("/greeting")
public class Greeting {
private String greeting;
public Greeting() {
this.setGreeting("hello");
}
@GET
@Produces(MediaType.TEXT_XML)
public Greeting sayHello() {
return new Greeting();
}
public String getGreeting() {
return greeting;
}
public void setGreeting(String greeting) {
this.greeting = greeting;
}
}
WebApp项目在嵌入式Tomcat v7服务器中运行(在eclipse中查看“Servers”).
请求：
http://localhost:8080/com.rest/greet/greeting
只要我使用MediaType.TEXT_XML就没有错误,内容如下所示：
<greeting>
<greeting>hello</greeting>
</greeting>
当我将MediaType更改为“MediaType.APPLICATION_JSON”时,将引发以下异常(如上所述).我已经注意到它取决于注释“@XmlRootElement”但是没有类似“JsonRootElement”的东西,并且jackson / genson API声称它开箱即用(由于自动注册机制).你知道怎么解决它吗？
非常感谢每一位帮助！
谢谢
golbie
解决方法:
您只需注册JacksonJsonProvider即可.有很多方法可以实现这一目标：
>在web.xml中明确注册JacksonJsonProvider：
<init-param>
<param-name>jersey.config.server.provider.classnames</param-name>
<param-value>com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider</param-value>
</init-param>
要么
>在web.xml中注册扩展javax.ws.rs.core.Application的类
<init-param>
<param-name>javax.ws.rs.Application</param-name>
<param-value>com.rest.MyApplication</param-value>
</init-param>
然后执行应用程序类中的所有配置：
package com.rest;
import org.glassfish.jersey.server.ResourceConfig;
import com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider;
public class MyApplication extends ResourceConfig {
public MyApplication() {
packages("com.rest");
register(JacksonJsonProvider.class);
}
ResourceConfig是javax.ws.rs.Application的子类,它为您提供了一些帮助您轻松注册的辅助方法.
要么
>使用自动注册.只需将依赖项添加到jersey-media-json-jackson即可
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-jackson</artifactId>
<version>2.13</version>
</dependency>
不过要小心.它将注册超过您需要的：
> JacksonJaxbJson提供者,
> JsonParseExceptionMapper,
> JsonMappingExceptionMapper
看看source code看看它的作用.