泽西岛+ App Engine项目启动错误

Question

Did a lot of search, but no luck.

I'm trying to make a 'hello world' app which integrates Jersey and Google App Engine. In Eclipse, I created a 'Web Application Project' and added Jersey JAR to the build path. Then I modified web.xml and it looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
    <servlet-name>Jersey Web Application</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.example.myJersey</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>Jersey Web Application</servlet-name>
    <url-pattern>/*</url-pattern>
</servlet-mapping>

In the package 'com.example.myJersey' I have HelloWorldResource.java, here is an excerpt:

// The Java class will be hosted at the URI path "/helloworld"
@Path("/helloworld")
public class HelloWorldResource {

    // The Java method will process HTTP GET requests
    @GET 
    // The Java method will produce content identified by the MIME Media
    // type "text/plain"
    @Produces("text/plain")
    public String getClichedMessage() {
        // Return some cliched textual content
        return "Hello World";
    }
}

When I click run, I get this error:

INFO: Successfully processed C:\Users\upelsin\wtf-rest\war\WEB-INF/web.xml
фев 02, 2012 5:05:16 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: failed Jersey Web Application: java.lang.IncompatibleClassChangeError: Implementing class
фев 02, 2012 5:05:16 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: failed com.google.appengine.tools.development.DevAppEngineWebAppContext@1aa58969{/,C:\Users\upelsin\wtf-rest\war}: java.lang.IncompatibleClassChangeError: Implementing class
фев 02, 2012 5:05:16 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: failed JettyContainerService$ApiProxyHandler@6d26b88a:  java.lang.IncompatibleClassChangeError: Implementing class
фев 02, 2012 5:05:16 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: Error starting handlers
java.lang.IncompatibleClassChangeError: Implementing class
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:176)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.sun.jersey.api.core.ScanningResourceConfig.init(ScanningResourceConfig.java:79)
at com.sun.jersey.api.core.servlet.WebAppResourceConfig.init(WebAppResourceConfig.java:102)
at com.sun.jersey.api.core.servlet.WebAppResourceConfig.<init>(WebAppResourceConfig.java:89)
at com.sun.jersey.api.core.servlet.WebAppResourceConfig.<init>(WebAppResourceConfig.java:74)
at com.sun.jersey.spi.container.servlet.WebComponent.getWebAppResourceConfig(WebComponent.java:672)
at com.sun.jersey.spi.container.servlet.ServletContainer.getDefaultResourceConfig(ServletContainer.java:414)
at com.sun.jersey.spi.container.servlet.ServletContainer.getDefaultResourceConfig(ServletContainer.java:581)
at com.sun.jersey.spi.container.servlet.WebServletConfig.getDefaultResourceConfig(WebServletConfig.java:87)
at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:703)
at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:678)
at com.sun.jersey.spi.container.servlet.WebComponent.init(WebComponent.java:203)
at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:373)
at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:556)

EDIT: Maybe there is a misconfiguration in web.xml. Looks like Jetty doesn't like Jersey's servlet class.

I would appreciate any kind of help.

Answer 1

I recently put together a project template on GitHub combining Jersey and Guice for AppEngine. It may help to compare with a running app.

Answer 2

Jersey requires Java 1.6. Is this what the Google App Engine runs on? Maybe your Google App instance is configured to run on an earlier Java version.

Answer 3

Look at this:

http://code.google.com/p/googleappengine/wiki/WillItPlayInJava

Make sure that you run Jersey 1.5 and configure as required in the doc. Also, are you using other libraries? Those may create a classloading conflict?