问题
I am following this tutorial to create a CRUD RESTful WebService.
The tutorial for this type of WebService starts in paragraph 7. I create the Server and the Client.
The Server seems to work perfectly fine as i do what the author suggests to test it and everything works as expected.
However , the Client gives me a hard time. When i run it i always get this error:
201
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><todoes><todo><id>3</id><summary>Blabla</summary></todo><todo><description>Read complete http://www.vogella.com</description><id>2</id><summary>Do something</summary></todo><todo><description>Read http://www.vogella.com/articles/REST/article.html</description><id>1</id><summary>Learn REST</summary></todo></todoes>
Exception in thread "main" com.sun.jersey.api.client.UniformInterfaceException: GET http://localhost:8080/CRUDserver/rest/todos returned a response status of 500 Internal Server Error
at com.sun.jersey.api.client.WebResource.handle(WebResource.java:686)
at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74)
at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:507)
at es.unican.cityInfo.client.Tester.main(Tester.java:34)
What exactly is the problem i cant understand ? Any ideas ?
The only assumption i can make , is based in this phrase of the author , in the beginning of building the client :
Create a new Java project called de.vogella.jersey.todo.client. Create a lib folder and place all jersey libs in this folder. Add the jars to the classpath of the project.
He says to place all jersey libs inside a folder. However what are these libs???
The only thing i have for the client are 2 jar files : jersey-client.jar and jersey-core.jar which i found on the site of jersey...
As suggested here is the log from the server , when i run the client :
Apr 26, 2013 5:46:19 PM com.sun.jersey.spi.container.ContainerResponse write
SEVERE: A message body writer for Java class java.util.ArrayList, and Java type java.util.List<es.unican.cityInfo.model.Todo>, and MIME media type application/json was not found
Apr 26, 2013 5:46:19 PM com.sun.jersey.spi.container.ContainerResponse write
SEVERE: 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
Apr 26, 2013 5:46:19 PM com.sun.jersey.spi.container.ContainerResponse logException
SEVERE: Mapped exception to response: 500 (Internal Server Error)
javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message body writer for Java class java.util.ArrayList, and Java type java.util.List<es.unican.cityInfo.model.Todo>, 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:1479)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1391)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1381)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:538)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:716)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:662)
Caused by: com.sun.jersey.api.MessageException: A message body writer for Java class java.util.ArrayList, and Java type java.util.List<es.unican.cityInfo.model.Todo>, and MIME media type application/json was not found
... 24 more
回答1:
Since you are getting a 500 error, this means the code is erroring on the server side. You will have to look at the log on the server side to figure out what went wrong.
HTTP Status Codes are meant to give you information about the request.
See here
EDIT:
So it appears that your return type on the method being mapped to that HTTP request is JSON, but you have not registered a JSON message writer for Jersey to use.
回答2:
Probably the simples way is to use Jersey's POJO support feature. To enable it, add the JSONConfiguration.FEATURE_POJO_MAPPING init parameter to the servlet configuration of your web.xml:
<servlet>
<servlet-name>jersey-serlvet</servlet-name>
<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
...
<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>
You will probably need to add a couple of jar's in addition to the ones you already have. Check this link for a list of the dependencies: https://jersey.java.net/nonav/documentation/latest/chapter_deps.html#d4e1828
回答3:
Caused by: com.sun.jersey.api.MessageException: A message body writer for Java class java.util.ArrayList, and Java type java.util.List, and MIME media type application/json was not found
I think your es.unican.cityInfo.model.Todo class is missing the following annotation @XmlRootElement
i.e.
package de.vogella.jersey.jaxb.model;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement // never forget me
// JAX-RS supports an automatic mapping from JAXB annotated class to XML and JSON
// Isn't that cool?
public class Todo {
private String summary;
private String description;
public String getSummary() {
return summary;
}
public void setSummary(String summary) {
this.summary = summary;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
来源：https://stackoverflow.com/questions/16240637/errors-while-trying-to-make-a-restful-webservice-with-jersey