Jersey Web服务提供了javax.servlet.ServletException：

Question

OK I have a problem with my web service.

I am trying to make an API for a user but after I have deployed the app and try to GET all users it gives me an exception.

Here is my api class:

package api;


import java.util.ArrayList;

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

import model.UserManager;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import dto.User;

@Path("/user")
public class UserAPI {

    @POST 
    @Path("create-user/{user}")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response saveUser(@PathParam("user") User user) throws JSONException {
        UserManager userManager = new UserManager();
        userManager.createUser(user);

        return Response.status(200).build();    
    }

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public JSONObject getAllUsers() throws JSONException {
        JSONObject users = null;
        try {
            ArrayList<User> usersList = null;
            UserManager userManager = new UserManager();
            usersList = userManager.getUsers();
            JSONObject usersObject = new JSONObject();
            for(int i = 0; i < usersList.size(); i++) {
                usersObject.put("users", usersList);
            }
            users = usersObject;
        } catch(Exception e) {
            e.printStackTrace();
        }
        return users;   
    }

    @POST 
    @Path("edit-user/{id}")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response editUser(@PathParam("id") int id) throws JSONException {
        UserManager userManager = new UserManager();
        userManager.editUser(id);

        return Response.status(200).build();    
    }

    @POST 
    @Path("delete-user/{id}")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response deleteUser(@PathParam("id") int id) throws JSONException {
        UserManager userManager = new UserManager();
        userManager.deleteUser(id);

        return Response.status(200).build();    
    }

    @POST 
    @Path("user-login/{user}")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response userLogin(@PathParam("user") User user) throws JSONException {
        UserManager userManager = new UserManager();
        userManager.userLogin(user);

        return Response.status(200).build();    
    }
}

Here is the error log:

javax.servlet.ServletException: Servlet.init() for servlet Jersey REST Service threw exception
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:683)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:745)

com.sun.jersey.spi.inject.Errors$ErrorMessagesException
    com.sun.jersey.spi.inject.Errors.processErrorMessages(Errors.java:170)
    com.sun.jersey.spi.inject.Errors.postProcess(Errors.java:136)
    com.sun.jersey.spi.inject.Errors.processWithErrors(Errors.java:199)
    com.sun.jersey.server.impl.application.WebApplicationImpl.initiate(WebApplicationImpl.java:795)
    com.sun.jersey.server.impl.application.WebApplicationImpl.initiate(WebApplicationImpl.java:790)
    com.sun.jersey.spi.container.servlet.ServletContainer.initiate(ServletContainer.java:491)
    com.sun.jersey.spi.container.servlet.ServletContainer$InternalWebComponent.initiate(ServletContainer.java:321)
    com.sun.jersey.spi.container.servlet.WebComponent.load(WebComponent.java:605)
    com.sun.jersey.spi.container.servlet.WebComponent.init(WebComponent.java:207)
    com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:376)
    com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:559)
    javax.servlet.GenericServlet.init(GenericServlet.java:158)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:683)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.lang.Thread.run(Thread.java:745)

Answer 1

Why dont you return the list of users as is instead of converting it into a json object? Try this:

@GET
@Produces(MediaType.APPLICATION_JSON)
public List<User> getAllUsers() {
    JSONObject users = null;
    try {
        ArrayList<User> usersList = null;
        UserManager userManager = new UserManager();
        usersList = userManager.getUsers();
    } catch(Exception e) {
        e.printStackTrace();
    }
    return usersList;   
}

And to invoke the above method from your view, you can use the follwing jquery ajax call:

$.ajax({
type: "GET",
url: "http://localhost:8080/YourProjectName/rest/user",
dataType: "json",
success: function(jsonString) {
   alert(jsonString);
},
error: function(xhr) {                     
    alert(JSON.stringify(xhr));
}

});

If it's still not working, then it can be an issue with the set of libraries that you are using. Hence I suggest you to use GlassFish 4.0 application server instead of Tomcat server. If you use GlassFish server, you must not include any jersey jar in your classpath as GlassFish server itself has all jersey related jars.

Answer 2

First of all, you want to submit a User object as a PathParam. This will not work!
Also i would like to suggest you, to make UserManager a Singleton.
Than, you should use GET, PUT, POST, DELETE and not just GET and POST

I think the exception says that you have made a mistake in your web.xml and jersey is'nt able to find the (or any) @Path. Therefore, pls give us the web.xml to prove that and you pom.xml to check that too.

Btw, jersey brings (un)marshallers, don't see a reason to use JSONObject.

Here some stuff:

simple web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <!-- not required with servlet 3.x -->
    <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <servlet>
        <servlet-name>REST</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>path.to.ResourceConfigOrApplication</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>REST</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

pom.xml (partly)

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.plugin.version>2.5.1</maven.compiler.plugin.version>
    <tomcat7.version>2.1</tomcat7.version>
    <jersey.version>2.12</jersey.version>
</properties>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.glassfish.jersey</groupId>
            <artifactId>jersey-bom</artifactId>
            <version>${jersey.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>
<dependencies>
    <!-- JERSEY -->
    <dependency>
        <groupId>org.glassfish.jersey.core</groupId>
        <artifactId>jersey-server</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.bundles</groupId>
        <artifactId>jaxrs-ri</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-json-processing</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-json-jackson</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-multipart</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-moxy</artifactId>
    </dependency> 
    // ...

Very Simple User:

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class User implements Serializable {

    private static final long serialVersionUID = 1L;

    @XmlElement(name="id")
    private Integer id;

    @XmlElement(name="username")
    private String username;

    // ...
}

And the simple resource (based on yours):

@Path("/users") // changed from user to users 
public class UserAPI {

    @POST 
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response saveUser(User user) {
        user = UserManager.getInstance().createUser(user);
        return Response.ok(user).build();    
    }

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response getAllUsers() {
        List<User> users = UserManager.getInstance().getUsers();
        GenericEntity<List<User>> entity = new GenericEntity<List<User>>(
            users
        ){};
        return Response.ok( entity ).build();
    }

    @PUT // edit-user -> PUT 
    @Path("/{id}")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response editUser(@PathParam("id") Integer id, User user) {
        user = UserManager.getInstance().editUser(id, user); // check id and uder.id, if user exists etc
        return Response.ok(user).build();
    }

    @DELETE // delete-user -> DELETE
    @Path("/{id}")
    @Produces(MediaType.APPLICATION_JSON)
    public Response deleteUser(@PathParam("id") Integer id) {
        UserManager.getInstance().deleteUser(id);
        return Response.ok().build();    
    }
}