尝试将自定义对象转换为 json 时的 Jersey 异常答案

【问题标题】：Jersey Exception when trying to convert a custom object to json尝试将自定义对象转换为 json 时的 Jersey 异常
【发布时间】：2016-08-17 14:57:32
【问题描述】：

在你们将此问题标记为重复之前，我想告诉你们，我已经尝试了来自

的解决方案

A message body writer for Java class not found

javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: JSON support in Java REST Webservices with Jersey

https://www.nabisoft.com/tutorials/java-ee/producing-and-consuming-json-or-xml-in-java-rest-services-with-jersey-and-jackson

我还是被困住了。这是我遇到的例外。

24-Apr-2016 02:03:00.655 SEVERE [http-nio-8080-exec-1] com.sun.jersey.spi.container.ContainerResponse.write A message body writer for Java class com.upwork.magnus.model.FirstException, and Java type class com.upwork.magnus.model.FirstException, and MIME media type application/json was not found
24-Apr-2016 02:03:00.656 SEVERE [http-nio-8080-exec-1] com.sun.jersey.spi.container.ContainerResponse.write The registered message body writers compatible with the MIME media type are:
*/* ->
  com.sun.jersey.core.impl.provider.entity.FormProvider
  com.sun.jersey.core.impl.provider.entity.StringProvider
  com.sun.jersey.core.impl.provider.entity.ByteArrayProvider
  com.sun.jersey.core.impl.provider.entity.FileProvider
  com.sun.jersey.core.impl.provider.entity.InputStreamProvider
  com.sun.jersey.core.impl.provider.entity.DataSourceProvider
  com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$General
  com.sun.jersey.core.impl.provider.entity.ReaderProvider
  com.sun.jersey.core.impl.provider.entity.DocumentProvider
  com.sun.jersey.core.impl.provider.entity.StreamingOutputProvider
  com.sun.jersey.core.impl.provider.entity.SourceProvider$SourceWriter
  com.sun.jersey.server.impl.template.ViewableMessageBodyWriter
  com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$General

24-Apr-2016 02:03:00.656 SEVERE [http-nio-8080-exec-1] com.sun.jersey.spi.container.ContainerResponse.logException Mapped exception to response: 500 (Internal Server Error)
 javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message body writer for Java class com.upwork.magnus.model.FirstException, and Java type class com.upwork.magnus.model.FirstException, and MIME media type application/json was not found
    at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:285)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1437)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: com.sun.jersey.api.MessageException: A message body writer for Java class com.upwork.magnus.model.FirstException, and Java type class com.upwork.magnus.model.FirstException, and MIME media type application/json was not found
    ... 29 more

这里是pom.xml文件依赖文件

<dependencies>
    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-server</artifactId>
        <version>1.8</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.9</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>eclipselink</artifactId>
        <version>2.5.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>
    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-json</artifactId>
        <version>1.9.1</version>
    </dependency>
    <dependency>
        <groupId>joda-time</groupId>
        <artifactId>joda-time</artifactId>
        <version>2.9.1</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.7.0</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-core-asl</artifactId>
        <version>1.9.9</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-jaxrs</artifactId>
        <version>1.9.9</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>1.9.9</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-xc</artifactId>
        <version>1.9.9</version>
    </dependency>

    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>3.8.1</version>
        <scope>test</scope>
    </dependency>
</dependencies>

这是我试图返回对象的行

    public Response response() throws JsonProcessingException {
        if (fe != null){
            return Response.status(Response.Status.BAD_REQUEST)
                    .entity(fe)
                    .type(MediaType.APPLICATION_JSON)
                    .build();
        }
        return null;
    }

fe 对象的类型为 FirstException。这是那个类

public class FirstException implements Serializable{
    private int errorCode;
    private String message;

    public FirstException(int errorCode, String message) {
        this.errorCode = errorCode;
        this.message = message;
    }

    public String getMessage() {
        return message;
    }

    public int getErrorCode() { return errorCode;}
}

这是我的 web.xml 部分来配置 pojo

<servlet>
    <servlet-name>jersey-servlet</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
    <init-param>
        <param-name>com.sun.jersey.config.property.packages</param-name>
        <param-value>com.upwork.magnus.api</param-value>
    </init-param>
    <init-param>
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

我尝试按照少数人的建议从我的pom.xml 文件中删除除jersey-json 之外的所有内容，但问题仍然相同。这是pom.xml

<dependencies>
    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-server</artifactId>
        <version>1.8</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.9</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>eclipselink</artifactId>
        <version>2.5.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>
    <dependency>
        <groupId>com.sun.jersey</groupId>
        <artifactId>jersey-json</artifactId>
        <version>1.9.1</version>
    </dependency>
    <dependency>
        <groupId>joda-time</groupId>
        <artifactId>joda-time</artifactId>
        <version>2.9.1</version>
    </dependency>

【问题讨论】：

为什么 FlightException 不是 Exception 子类？
抱歉，这只是我使用的名称。很可能会更改为ErrorResponse。
你应该做的第一件事是摆脱你在 pom 文件中的 everything jackson。 jersey-json 拉入您需要的杰克逊。你无缘无故地拥有所有这些不同版本的不同东西。
已删除并尝试过。同样的问题。我将在我的问题中发布更新的 pom.xml。谢谢
您可以将@XmlRootElement 添加到FirstException 类中。它应该工作。但这对于根本问题来说确实是一种不受欢迎的解决方法，即“为什么不使用杰克逊”。查看错误，如果查看提供程序列表，则看不到 Jackson。我不知道为什么。

标签： java json rest jersey jackson

【解决方案1】：

如果您查看错误，您将看到 Jackson json 提供程序不是注册的提供程序之一。只有默认的 Jersey 是使用 JAXB 功能的。所以你可以用@XmlRootElement注释FirstException类，它应该可以工作。但这确实是解决潜在问题的一种不受欢迎的解决方法，即“为什么不使用杰克逊？”。

您可以确保使用 Jackson 的方法是将 org.codehaus.jackson.jaxrs 包添加到要扫描的包列表中。此包包含 Jackson json 提供程序。

<init-param>
    <param-name>com.sun.jersey.config.property.packages</param-name>
    <param-value>
        com.upwork.magnus.api,
        org.codehaus.jackson.jaxrs
    </param-value>
</init-param>

【讨论】：