我一直在尝试制作某个API，并且需要它以JSON格式显示服务器上方法的结果。如果我尝试简单
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
@Path("/messages")
public class MessageResource {
@GET
@Produces(MediaType.TEXT_PLAIN)
public String getMessages() {
return "Hello World!";
}
}
它可以工作，但是当我尝试使用以JSON格式返回值的类时，它在服务器上显示了一些错误（它在普通控制台中工作）。
我对此并不陌生，希望我能解释得足够好。
type Exception report
message org.glassfish.jersey.server.ContainerException: java.lang.NoClassDefFoundError: org/codehaus/jackson/map/ObjectMapper
description The server encountered an internal error that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: org.glassfish.jersey.server.ContainerException: java.lang.NoClassDefFoundError: org/codehaus/jackson/map/ObjectMapper
org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:489)
org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:427)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:388)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:341)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:228)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
org.glassfish.jersey.server.ContainerException: java.lang.NoClassDefFoundError: org/codehaus/jackson/map/ObjectMapper
org.glassfish.jersey.servlet.internal.ResponseWriter.rethrow(ResponseWriter.java:278)
org.glassfish.jersey.servlet.internal.ResponseWriter.failure(ResponseWriter.java:260)
org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:509)
org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:334)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
org.glassfish.jersey.internal.Errors.process(Errors.java:315)
org.glassfish.jersey.internal.Errors.process(Errors.java:297)
org.glassfish.jersey.internal.Errors.process(Errors.java:267)
org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:305)
org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1154)
org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:473)
org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:427)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:388)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:341)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:228)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
java.lang.NoClassDefFoundError: org/codehaus/jackson/map/ObjectMapper
valendor.messenger.ReturnJson.main(ReturnJson.java:27)
sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:144)
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:161)
org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$VoidOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:143)
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:99)
org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:326)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
org.glassfish.jersey.internal.Errors.process(Errors.java:315)
org.glassfish.jersey.internal.Errors.process(Errors.java:297)
org.glassfish.jersey.internal.Errors.process(Errors.java:267)
org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:305)
org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1154)
org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:473)
org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:427)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:388)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:341)
org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:228)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.36 logs.
多数民众赞成在错误
最佳答案
显然，如错误消息所示，您缺少org.codehaus.jackson.map.ObjectMapper类。您必须将jackson-mapper库添加到类路径中，即添加到WEB-INF/lib文件夹中。
如果使用Maven构建项目，则将以下依赖项添加到pom.xml：
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-lgpl</artifactId>
<version>1.9.13</version>
</dependency>
（将版本替换为您要使用的版本，1.9.13是最新的ATM）