带有servlet的Java Guice在“主”线程中异常java.lang.NoClassDefFoundError：com / google / inject / internal / util / $ Preconditions

Question

我正在尝试使用Google App Engine配置Guice，但是在启动服务器时（使用“ gradle appengineRun”）出现此问题：

Exception in thread "main" java.lang.NoClassDefFoundError: com/google/inject/internal/util/$Preconditions
    at com.google.inject.servlet.ServletModule.configure(ServletModule.java:44)
    at com.google.inject.AbstractModule.configure(AbstractModule.java:62)
    at com.google.inject.spi.Elements$RecordingBinder.install(Elements.java:340)
    at com.google.inject.spi.Elements.getElements(Elements.java:110)
    at com.google.inject.internal.InjectorShell$Builder.build(InjectorShell.java:138)
    at com.google.inject.internal.InternalInjectorCreator.build(InternalInjectorCreator.java:104)
    at com.google.inject.Guice.createInjector(Guice.java:96)
    at com.google.inject.Guice.createInjector(Guice.java:73)
    at com.google.inject.Guice.createInjector(Guice.java:62)
    at MyGuiceServletConfig.getInjector(MyGuiceServletConfig.java:17)
    at com.google.inject.servlet.GuiceServletContextListener.contextInitialized(GuiceServletContextListener.java:45)
    at org.eclipse.jetty.server.handler.ContextHandler.callContextInitialized(ContextHandler.java:843)
    at org.eclipse.jetty.servlet.ServletContextHandler.callContextInitialized(ServletContextHandler.java:533)
    at org.eclipse.jetty.server.handler.ContextHandler.startContext(ContextHandler.java:816)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:345)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1406)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1368)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:778)
    at org.eclipse.jetty.servlet.ServletContextHandler.doStart(ServletContextHandler.java:262)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:522)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:131)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:105)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:131)
    at org.eclipse.jetty.server.Server.start(Server.java:422)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:105)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:389)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at com.google.appengine.tools.development.jetty9.JettyContainerService.startContainer(JettyContainerService.java:346)
    at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:284)
    at com.google.appengine.tools.development.AutomaticInstanceHolder.startUp(AutomaticInstanceHolder.java:26)
    at com.google.appengine.tools.development.AbstractModule.startup(AbstractModule.java:87)
    at com.google.appengine.tools.development.Modules.startup(Modules.java:105)
    at com.google.appengine.tools.development.DevAppServerImpl.doStart(DevAppServerImpl.java:274)
    at com.google.appengine.tools.development.DevAppServerImpl.access$000(DevAppServerImpl.java:47)
    at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:219)
    at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:217)
    at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:368)
    at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:47)
    at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:223)
    at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:214)
Caused by: java.lang.ClassNotFoundException: com.google.inject.internal.util.$Preconditions
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:196)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 46 more

项目结构：

服务器和基础结构部分仅包含一些DAO和Factory元素

web.xml：

<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
     version="2.5">
<!--<servlet>-->
    <!--<servlet-name>hello</servlet-name>-->
    <!--<servlet-class>Main</servlet-class>-->
<!--&lt;!&ndash;</servlet>&ndash;&gt;-->
<!--<servlet-mapping>-->
    <!--<servlet-name>hello</servlet-name>-->
    <!--<url-pattern>/data</url-pattern>-->
<!--</servlet-mapping>-->
<listener>
    <listener-class>
        MyContextListener
    </listener-class>

</listener>
<listener>
    <listener-class>MyGuiceServletConfig</listener-class>
</listener>
</web-app>

MyContextListener应该使用一些初始数据加载数据库，并且可以正常工作，但是我不知道是否可以将其与MyGuiceServletConfig一起使用。

MyGuiceServletConfig.java：

import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Provides;
import com.google.inject.name.Named;
import com.google.inject.name.Names;
import com.google.inject.servlet.GuiceServletContextListener;
import com.google.inject.servlet.RequestScoped;
import com.google.inject.servlet.ServletModule;
import edu.ubb.cs.idde.DAO.EmployeeDAOHibernatePersistence;
import edu.ubb.cs.idde.DAO.EmployeesDAO;
import edu.ubb.cs.idde.Employees.Employee;

public class MyGuiceServletConfig extends GuiceServletContextListener {

@Override
protected Injector getInjector() {
    return Guice.createInjector(new ServletModule(){

        @Override
        protected void configureServlets(){
            serve("/data").with(Main.class);
            bind(EmployeesDAO.class).annotatedWith(Names.named("HibernatePersistence")).to(EmployeeDAOHibernatePersistence.class);
        }

    });

}

}

Main.java：

import com.google.gson.Gson;
import com.google.inject.Inject;
import com.google.inject.name.Named;
import edu.ubb.cs.idde.DAO.EmployeeDAOHibernatePersistence;
import edu.ubb.cs.idde.DAO.EmployeesDAO;
import edu.ubb.cs.idde.DAO.EmployeesDAOHibernate;
import edu.ubb.cs.idde.Employees.Employee;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.inject.Singleton;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@Singleton
public class Main extends HttpServlet {
EmployeesDAO empl;

@Inject
Main(EmployeesDAO employeesDAO)
{
    this.empl = new EmployeeDAOHibernatePersistence();
}


@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    PrintWriter out = resp.getWriter();
    Gson gson = new Gson();
    List<Object> list = empl.readAllEmployees();
    out.println(gson.toJson(list));
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) 
throws ServletException, IOException {
    PrintWriter out = resp.getWriter();
    Gson gson = new Gson();
//        int ID = 
Integer.parseInt(String.valueOf(req.getParameterValues("ID")));
    String first = String.valueOf(req.getParameterValues("First"));
    String last = String.valueOf(req.getParameterValues("Last"));
    int age = 
Integer.parseInt(String.valueOf(req.getParameterValues("Age")));
    empl.createEmployee(new Employee(first,last,age));
    out.println("OK");
}

@Override
protected void doPut(HttpServletRequest req, HttpServletResponse resp) 
throws ServletException, IOException {
    PrintWriter out = resp.getWriter();
    Gson gson = new Gson();
    int ID = Integer.parseInt(String.valueOf(req.getParameterValues("ID")));
    String first = String.valueOf(req.getParameterValues("First"));
    String last = String.valueOf(req.getParameterValues("Last"));
    int age = 
Integer.parseInt(String.valueOf(req.getParameterValues("Last")));
    empl.updateEmployee(new Employee(first,last,age));
    out.println("OK");
}

@Override
protected void doDelete(HttpServletRequest req, HttpServletResponse resp) 
throws ServletException, IOException {
    PrintWriter out = resp.getWriter();
    Gson gson = new Gson();
    int ID = Integer.parseInt(String.valueOf(req.getParameterValues("ID")));
    String first = String.valueOf(req.getParameterValues("First"));
    String last = String.valueOf(req.getParameterValues("Last"));
    int age = 
Integer.parseInt(String.valueOf(req.getParameterValues("Last")));
    empl.deleteEmployee(new Employee(first,last,age));
    out.println("OK");
}

}

Answer 1

基于其他类似 情况 ，您似乎正在使用过时的Guice版本，或者至少使用了Guice的扩展版本，而该版本与该库的其余部分版本不一致。

确保对Guice库及其扩展使用相同的版本（最新版本为4.1）。

无论如何，每当您部署应用程序时，请按照此处描述的步骤进行操作。