rest - Spring 4 RestController JSON : characteristics not acceptable according to the request "accept" headers

Question

我正在使用 spring 4.1.1.RELEASE 并包括: pom 中的 jackson-core-asl 1.9.13 和 jackson-mapper-asl 1.9.13 来创建一个带有 RestController 的简单应用程序。

这是 repo :https://github.com/robikshrestha/samplespringrest.git

这是失败的 war :https://github.com/robikshrestha/samplespringrest/tree/master/failingWar

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.mycompany</groupId>
    <artifactId>SampleContactApp</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>SampleContactApp</name>

    <properties>
        <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring.version>4.1.1.RELEASE</spring.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>


        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
        </dependency>


        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-asl</artifactId>
            <version>1.9.13</version>
        </dependency>

        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-core-asl</artifactId>
            <version>1.9.13</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <compilerArguments>
                        <endorseddirs>${endorsed.dir}</endorseddirs>
                    </compilerArguments>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.3</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.6</version>
                <executions>
                    <execution>
                        <phase>validate</phase>
                        <goals>
                            <goal>copy</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${endorsed.dir}</outputDirectory>
                            <silent>true</silent>
                            <artifactItems>
                                <artifactItem>
                                    <groupId>javax</groupId>
                                    <artifactId>javaee-endorsed-api</artifactId>
                                    <version>7.0</version>
                                    <type>jar</type>
                                </artifactItem>
                            </artifactItems>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

这是我的 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" version="2.5">
    <servlet>
        <servlet-name>sample</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>sample</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

和我的 sample-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc" 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <context:component-scan base-package="com.sample" />
    <mvc:annotation-driven />
</beans>

Controller 类也很简单。 Sample 类确实有公共(public)的 getter 和 setter。

@RestController
@RequestMapping("/")
public class SampleController {

    @RequestMapping("/getSample")
    public Sample getSample() {
        Sample s = new Sample();
        s.setId(1);
        s.setName("abc");
        return s;
    }
}

当我通过浏览器发送请求时，我得到，

The resource identified by this request is only capable of generating responses with characteristics not acceptable according to the request "accept" headers.

我尝试使用 header 作为其他 REST 工具发送请求

Accept:application/json

甚至尝试过 $.getJSON()、$.ajax() 等。
，但仍然出现相同的错误。我已经尝试过 StackOverflow 中的所有其他相关线程，但问题仍然存在。

Answer 1

这个错误的诀窍是它可能非常容易误导。在与 OP 一样的情况下，您会看到由浏览器 GET 请求(使用 accept header */* )和正确配置(在 OPs 情况下为默认的最小工作配置)导致的错误，原因很可能是异常，而转换为表示。

在这里，即使请求没有建议表示(也不是参数，也不是路径，也不是接受 header )，但响应却在提示

resource identified by this request is only capable of generating responses with characteristics not acceptable according to the request "accept" headers

原因可能是:

缺少的依赖项

返回 bean 中的错误
(例如缺少 setter/getter 等)

截至 Spring 框架 4.1 , 最低 jackson 版本应该是 2.1 (2.3 recommended) ，用这个单一的替换你的 jackson 依赖

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.1.2</version>
    </dependency>

在这种情况下阻碍调试的一件事是，在 tomcat 7.0.5x 版本中，此依赖项在 libs 中可用，这与以前的某些版本不同。所以你的代码在那个版本的tomcat中工作正常，就像它一样

Spring MVC 3.x 版本仍应使用

    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>1.9.13</version>
    </dependency>