java - HttpMediaTypeNotAcceptableException : Could not find acceptable representation spring mvc 4. 1.5 与 com.fasterxml 2.5.1

Question

帮助 - 我还能做些什么来修复这个错误？ org.springframework.web.HttpMediaTypeNotAcceptableException::找不到可接受的表示形式。

我认为我的项目配置正确，可以处理 json restful 请求。在过去的几天里，我阅读并应用了各种建议都无济于事。关于我还应该做哪些不同的事情，还有更多想法吗？

我正在使用 Spring MVC 4.1.5 和 com.fasterxml 2.5.1。

我的 pom.xml 的一部分

 <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.5.1</version>
    <type>bundle</type>
 </dependency>
 <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.5.1</version>
    <type>bundle</type>
 </dependency>
 <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.5.1</version>
    <type>bundle</type>
 </dependency>

这是我的 web.xml 的一部分

<!-- Creates the Spring Container shared by all Servlets and Filters -->
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<!-- Processes application requests -->
<servlet>
    <servlet-name>appServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            /WEB-INF/spring/appServlet/servlet-context.xml
        </param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>appServlet</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

这是我的 servlet-context.xml 的一部分

<!-- Enables the Spring MVC @Controller programming model -->
<annotation-driven />

<!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
<resources mapping="/resources/**" location="/resources/" />

<!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
<beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <beans:property name="prefix" value="/WEB-INF/views/" />
    <beans:property name="suffix" value=".jsp" />
</beans:bean>

<context:component-scan base-package="com.losgatos">
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice" />
</context:component-scan>   

这是我的 Controller

package com.losgatos.controllers;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.losgatos.User;

@RestController
@RequestMapping( "user" )
public class UserController { 

    @RequestMapping( value = "data", produces="application/json" )
    public User getUser(){
        return new User();
    }   
}

这里是User用户POJO

package com.losgatos;

import java.util.EnumSet;

public class User {

    public User(){
        id = 0;
        age = 22;
        name = "Titus Feng"; 
        alias = "tornado tie";
        roles = EnumSet.of( Role.NORMAL, Role.NEW );
    }

    private int id, age;
    private String name, alias;
    private EnumSet<Role> roles;

    //added getters and setters here

    public enum Role{
        NEW, NORMAL, ADMIN, MEMBER, DORMANT 
    }   
}

Answer 1

在您的 spring 上下文配置文件 (dispatcher-servlet.xml) 中，您有:

<context:component-scan base-package="com.losgatos">
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice" />
</context:component-scan>

并且您的 Controller 注释为:

@RestController
@RequestMapping( "user" )
public class UserController { 
...
}

您的 Controller 类根本不会加载到容器中。顺便说一句，根据您的异常消息:

I am getting the error

org.springframework.web.HttpMediaTypeNotAcceptableException:: Could not find acceptable representation.

如果您没有在上下文文件中注册以下内容，则会引发此异常:

• <mvc:annotation-driven /> (您尚未在上下文文件中注册)
• 如果需要的 JAR 不在类路径中，(您已经有了)
• 使用 ENUM 时，用 @JsonFormat(shape= JsonFormat.Shape.OBJECT) 注释您的 ENUM 类

编辑: 使用 Spring 4.0.1.RELEASE 和以下单个 JSON 依赖项测试对我来说工作正常:

com.fasterxml.jackson.core jackson 数据绑定(bind) 2.4.3

和 Controller 类:

@RestController
@RequestMapping("/u")
public class UserRestController {

    @RequestMapping( value = "/data", produces="application/json" )
    public RestUser getUser(){
        return new RestUser();
    } 
}

得到:

{"id":0,"age":22,"name":"Titus Feng","alias":"tornado tie","roles":["NEW","NORMAL"]}

建议， 改变这个:

<context:component-scan base-package="com.losgatos">
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice" />
</context:component-scan>

到:

<context:component-scan base-package="com.losgatos">
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.RestController" />
</context:component-scan>