Question

我正在开发一个宁静的网络服务，实际上我正在使用一个文件，但我想建立数据库连接，所以我可以从数据库而不是文件中获取数据，我试图制作数据库连接，但它没有工作，甚至野生动物服务器停止并停止部署项目。这是我正在使用的文件：

DBConnection.java文件

package com.TP6;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DBConnection {

 public static Connection dbCon;
 public Statement dbStmt;
 public ResultSet dbRst;

 public static Connection setDBConnection() throws SQLException {
 try {

 System.out.println("Inside DB Connection");

 Class.forName("com.mysql.jdbc.Driver");
 dbCon = DriverManager.getConnection(
 "jdbc:mysql://localhost:3306/usermangment",
 "root", "");

 } catch (ClassNotFoundException e)

 {
 System.out.println(e);
 }
 return dbCon;
 }

 public void getInsertResutlSet(String sqlQuery, Connection conn)
 throws SQLException {

 System.out.println(sqlQuery);
 String sqlquery = sqlQuery;
 dbCon = conn;
 try {

 dbStmt = dbCon.createStatement();
 dbStmt.executeUpdate(sqlquery);

 } catch (SQLException se) {
 System.out.println(se);
 }

 }

 public ResultSet getResutlSet(String sqlQuery, Connection conn)
 throws SQLException {

 System.out.println(sqlQuery);
 String sqlquery = sqlQuery;
 dbCon = conn;
 try {

 dbStmt = dbCon.createStatement();
 dbRst = dbStmt.executeQuery(sqlquery);

 } catch (SQLException se) {
 System.out.println(se);
 }
 return dbRst;
 }
}

userDao.java：使用文件来获取和插入数据

package com.TP6; 

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.util.ArrayList; 
import java.util.List; 

public class UserDao { 
   public List<User> getAllUsers(){ 
      List<User> userList = null; 
      try { 



         File file = new File("Users.dat"); 
         if (!file.exists()) { 
            User user = new User(1, "", ""); 
            userList = new ArrayList<User>(); 
            userList.add(user); 
            saveUserList(userList);   
         } 
         else{ 
            FileInputStream fis = new FileInputStream(file); 
            ObjectInputStream ois = new ObjectInputStream(fis); 
            userList = (List<User>) ois.readObject(); 
            ois.close(); 
         } 
      } catch (IOException e) { 
         e.printStackTrace(); 
      } catch (ClassNotFoundException e) { 
         e.printStackTrace(); 
      }   
      return userList; 
   } 

   public User getUser(int id){ 
      List<User> users = getAllUsers(); 

      for(User user: users){ 
         if(user.getId() == id){ 
            return user; 
         } 
      } 
      return null; 
   } 

   public int addUser(User pUser){ 
      List<User> userList = getAllUsers(); 
      boolean userExists = false; 
      for(User user: userList){ 
         if(user.getId() == pUser.getId()){ 
            userExists = true; 
            break; 
         } 
      }   
      if(!userExists){ 
         userList.add(pUser); 
         saveUserList(userList); 
         return 1; 
      } 
      return 0; 
   } 




   public int updateUser(User pUser){ 
      List<User> userList = getAllUsers(); 

      for(User user: userList){ 
         if(user.getId() == pUser.getId()){ 
            int index = userList.indexOf(user);    
            userList.set(index, pUser); 
            saveUserList(userList); 
            return 1; 
         } 
      }   
      return 0; 
   } 

   public int deleteUser(int id){ 
      List<User> userList = getAllUsers(); 

      for(User user: userList){ 
         if(user.getId() == id){ 
            int index = userList.indexOf(user);    
            userList.remove(index); 
            saveUserList(userList); 
            return 1;    
         } 
      }   
      return 0; 
   } 

   private void saveUserList(List<User> userList){ 
      try { 
         File file = new File("Users.dat"); 
         FileOutputStream fos; 

         fos = new FileOutputStream(file); 

         ObjectOutputStream oos = new ObjectOutputStream(fos);   
         oos.writeObject(userList); 
         oos.close(); 
      } catch (FileNotFoundException e) { 
         e.printStackTrace(); 
      } catch (IOException e) { 
         e.printStackTrace(); 
      } 
   } 
}

userService.java

 package com.TP6;     
import java.io.IOException; 
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List; 
import javax.servlet.http.HttpServletResponse; 
import javax.ws.rs.Consumes; 
import javax.ws.rs.DELETE; 
import javax.ws.rs.FormParam; 
import javax.ws.rs.GET; 
import javax.ws.rs.OPTIONS; 
import javax.ws.rs.POST; 
import javax.ws.rs.PUT; 


import javax.ws.rs.Path; 
import javax.ws.rs.PathParam; 
import javax.ws.rs.Produces; 
import javax.ws.rs.core.Context; 
import javax.ws.rs.core.MediaType; 

import com.TP6.DBConnection;
import com.mysql.jdbc.Connection;
@Path("/UserService") 
public class UserService { 

     DBConnection dbCoN;
     Connection conn;
     ResultSet rslt;
     String Iuser = "user inconnu ";
     String query;
   UserDao userDao = new UserDao(); 
   private static final String SUCCESS_RESULT="<result>success</result>"; 
   private static final String FAILURE_RESULT="<result>failure</result>"; 


   @GET
   @Path("/user/ID")
   @Produces(MediaType.APPLICATION_XML)
   public String Usernom(@PathParam("id") String id)

           throws SQLException {

   query = "select nom from user where id=55";

 //  System.out.println("" + query);
   dbCoN = new DBConnection();

   try {
   conn = (Connection) DBConnection.setDBConnection();
   rslt = dbCoN.getResutlSet(query, conn);

   if (rslt.next()) {

   String nom = rslt.getString(2);


   } else {
   return Iuser;
   }

   } catch (Exception e) {
   System.out.println(e);
   } finally {
   if (conn != null) {
   conn.close();
   }
   }

   return Iuser;

   }

   @GET 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   public List<User> getUsers(){ 
      return userDao.getAllUsers(); 
   } 

   @GET 
   @Path("/users/{userid}") 
   @Produces(MediaType.APPLICATION_XML) 
   public User getUser(@PathParam("userid") int userid){ 
      return userDao.getUser(userid); 
   } 

   @PUT 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   @Consumes(MediaType.APPLICATION_FORM_URLENCODED) 
   public String createUser(@FormParam("id") int id,@FormParam("nom") String nom,@FormParam("agence") String agence, @Context HttpServletResponse servletResponse) 
              throws IOException{ 
      User user = new User(id, nom, agence); 
      int result = userDao.addUser(user); 
      if(result == 1){ 
         return SUCCESS_RESULT; 
      } 
      return FAILURE_RESULT; 
   } 

   @POST 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   @Consumes(MediaType.APPLICATION_FORM_URLENCODED) 
   public String updateUser(@FormParam("id") int id, 
      @FormParam("nom") String nom, 
      @FormParam("agence") String agence, 
      @Context HttpServletResponse servletResponse) throws IOException{ 
      User user = new User(id, nom, agence); 
      int result = userDao.updateUser(user); 
      if(result == 1){ 
         return SUCCESS_RESULT; 
      } 
      return FAILURE_RESULT; 
   } 

   @DELETE 
   @Path("/users/{userid}") 
   @Produces(MediaType.APPLICATION_XML) 
   public String deleteUser(@PathParam("userid") int userid){ 
      int result = userDao.deleteUser(userid); 
      if(result == 1){ 
         return SUCCESS_RESULT; 
      } 
      return FAILURE_RESULT; 
   } 

   @OPTIONS 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   public String getSupportedOperations(){ 
      return "<operations>GET, PUT, POST, DELETE</operations>"; 
   } 
}

实际上我只想知道问题是什么，当我建立数据库连接时它停止工作。

这个控制台：

    20:26:51,986 INFO  [org.jboss.modules] (main) JBoss Modules version 1.3.0.Final
20:26:52,235 INFO  [org.jboss.msc] (main) JBoss MSC version 1.2.0.Final
20:26:52,327 INFO  [org.jboss.as] (MSC service thread 1-6) JBAS015899: WildFly 8.0.0.Final "WildFly" starting
20:26:53,805 INFO  [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 1) JBAS015003: Found UserManagment.war in deployment directory. To trigger deployment create a file called UserManagment.war.dodeploy
20:26:53,827 INFO  [org.jboss.as.server] (Controller Boot Thread) JBAS015888: Creating http management service using socket-binding (management-http)
20:26:53,856 INFO  [org.xnio] (MSC service thread 1-7) XNIO version 3.2.0.Final
20:26:53,868 INFO  [org.xnio.nio] (MSC service thread 1-7) XNIO NIO Implementation Version 3.2.0.Final
20:26:53,966 INFO  [org.jboss.as.connector.subsystems.datasources] (ServerService Thread Pool -- 28) JBAS010403: Deploying JDBC-compliant driver class org.h2.Driver (version 1.3)
20:26:53,976 INFO  [org.jboss.as.connector.subsystems.datasources] (ServerService Thread Pool -- 28) JBAS010404: Deploying non-JDBC-compliant driver class com.mysql.jdbc.Driver (version 5.1)
20:26:54,053 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 49) JBAS017502: Undertow 1.0.0.Final starting
20:26:54,037 INFO  [org.jboss.as.naming] (ServerService Thread Pool -- 41) JBAS011800: Activating Naming Subsystem
20:26:54,060 INFO  [org.jboss.as.security] (ServerService Thread Pool -- 46) JBAS013171: Activating Security Subsystem
20:26:54,061 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-2) JBAS017502: Undertow 1.0.0.Final starting
20:26:54,063 INFO  [org.jboss.as.security] (MSC service thread 1-2) JBAS013170: Current PicketBox version=4.0.20.Final
20:26:54,095 INFO  [org.jboss.as.webservices] (ServerService Thread Pool -- 50) JBAS015537: Activating WebServices Extension
20:26:54,099 INFO  [org.jboss.as.jsf] (ServerService Thread Pool -- 39) JBAS012615: Activated the following JSF Implementations: [main]
20:26:54,138 INFO  [org.jboss.as.clustering.infinispan] (ServerService Thread Pool -- 33) JBAS010280: Activating Infinispan subsystem.
20:26:54,180 INFO  [org.jboss.as.connector.logging] (MSC service thread 1-3) JBAS010408: Starting JCA Subsystem (IronJacamar 1.1.3.Final)
20:26:54,202 INFO  [org.jboss.as.naming] (MSC service thread 1-5) JBAS011802: Starting Naming Service
20:26:54,222 INFO  [org.jboss.as.connector.deployers.jdbc] (MSC service thread 1-2) JBAS010417: Started Driver service with driver-name = mysql
20:26:54,223 INFO  [org.jboss.as.connector.deployers.jdbc] (MSC service thread 1-2) JBAS010417: Started Driver service with driver-name = h2
20:26:54,214 INFO  [org.jboss.as.mail.extension] (MSC service thread 1-5) JBAS015400: Bound mail session [java:jboss/mail/Default]
20:26:54,505 INFO  [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-4) JBAS010400: Bound data source [java:/DsBibliotheque]
20:26:54,506 INFO  [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-4) JBAS010400: Bound data source [java:/DsBanque]
20:26:54,661 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 49) JBAS017527: Creating file handler for path C:\Users\Emel\wildfly-8.0.0.Final/welcome-content
20:26:54,689 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-4) JBAS017525: Started server default-server.
20:26:54,699 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-4) JBAS017531: Host default-host starting
20:26:54,781 INFO  [org.jboss.remoting] (MSC service thread 1-7) JBoss Remoting version 4.0.0.Final
20:26:54,981 INFO  [org.jboss.as.server.deployment.scanner] (MSC service thread 1-4) JBAS015012: Started FileSystemDeploymentService for directory C:\Users\Emel\wildfly-8.0.0.Final\standalone\deployments
20:26:54,987 INFO  [org.jboss.as.server.deployment] (MSC service thread 1-7) JBAS015876: Starting deployment of "UserManagment.war" (runtime-name: "UserManagment.war")
20:26:55,191 INFO  [org.wildfly.extension.undertow] (MSC service thread 1-8) JBAS017519: Undertow HTTP listener default listening on localhost/127.0.0.1:8180
20:26:55,399 INFO  [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-6) JBAS010400: Bound data source [java:jboss/datasources/ExampleDS]
20:26:55,728 INFO  [org.jboss.ws.common.management] (MSC service thread 1-8) JBWS022052: Starting JBoss Web Services - Stack CXF Server 4.2.3.Final
20:26:56,055 ERROR [org.jboss.remoting.remote.connection] (XNIO-1 I/O-1) JBREM000200: Remote connection failed: java.io.IOException: Une connexion établie a été abandonnée par un logiciel de votre ordinateur hôte
20:26:56,057 ERROR [org.jboss.remoting.remote.connection] (XNIO-1 I/O-2) JBREM000200: Remote connection failed: java.io.IOException: Une connexion établie a été abandonnée par un logiciel de votre ordinateur hôte
20:26:56,571 INFO  [org.jboss.resteasy.spi.ResteasyDeployment] (MSC service thread 1-3) Deploying javax.ws.rs.core.Application: class com.TP6.RestApplicationConfig
20:26:56,615 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-3) MSC000001: Failed to start service jboss.undertow.deployment.default-server.default-host./UserManagment: org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./UserManagment: Failed to start service
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1904) [jboss-msc-1.2.0.Final.jar:1.2.0.Final]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [rt.jar:1.8.0_91]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [rt.jar:1.8.0_91]
    at java.lang.Thread.run(Unknown Source) [rt.jar:1.8.0_91]
Caused by: java.lang.NoClassDefFoundError: Lcom/mysql/jdbc/Connection;
    at java.lang.Class.getDeclaredFields0(Native Method) [rt.jar:1.8.0_91]
    at java.lang.Class.privateGetDeclaredFields(Unknown Source) [rt.jar:1.8.0_91]
    at java.lang.Class.getDeclaredFields(Unknown Source) [rt.jar:1.8.0_91]
    at org.jboss.resteasy.spi.metadata.ResourceBuilder.processDeclaredFields(ResourceBuilder.java:867)
    at org.jboss.resteasy.spi.metadata.ResourceBuilder.processFields(ResourceBuilder.java:849)
    at org.jboss.resteasy.spi.metadata.ResourceBuilder.fromAnnotations(ResourceBuilder.java:755)
    at org.jboss.resteasy.spi.metadata.ResourceBuilder.rootResourceFromAnnotations(ResourceBuilder.java:700)
    at org.jboss.resteasy.plugins.server.resourcefactory.POJOResourceFactory.<init>(POJOResourceFactory.java:29)
    at org.jboss.resteasy.core.ResourceMethodRegistry.addPerRequestResource(ResourceMethodRegistry.java:75)
    at org.jboss.resteasy.spi.ResteasyDeployment.registration(ResteasyDeployment.java:400)
    at org.jboss.resteasy.spi.ResteasyDeployment.start(ResteasyDeployment.java:241)
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.init(ServletContainerDispatcher.java:112)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.init(HttpServletDispatcher.java:36)
    at io.undertow.servlet.core.ManagedServlet$DefaultInstanceStrategy.start(ManagedServlet.java:208)
    at io.undertow.servlet.core.ManagedServlet.createServlet(ManagedServlet.java:116)
    at io.undertow.servlet.core.DeploymentManagerImpl.start(DeploymentManagerImpl.java:496)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.startContext(UndertowDeploymentService.java:87)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.start(UndertowDeploymentService.java:71)
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1948) [jboss-msc-1.2.0.Final.jar:1.2.0.Final]
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1881) [jboss-msc-1.2.0.Final.jar:1.2.0.Final]
    ... 3 more
Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.Connection from [Module "deployment.UserManagment.war:main" from Service Module Loader]
    at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:197) [jboss-modules.jar:1.3.0.Final]
    at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:443) [jboss-modules.jar:1.3.0.Final]
    at org.jboss.modules.ConcurrentClassLoader.performLoadClassChecked(ConcurrentClassLoader.java:431) [jboss-modules.jar:1.3.0.Final]
    at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:373) [jboss-modules.jar:1.3.0.Final]
    at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:118) [jboss-modules.jar:1.3.0.Final]
    ... 23 more

20:26:56,630 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) JBAS014613: Operation ("deploy") failed - address: ([("deployment" => "UserManagment.war")]) - failure description: {"JBAS014671: Failed services" => {"jboss.undertow.deployment.default-server.default-host./UserManagment" => "org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./UserManagment: Failed to start service
    Caused by: java.lang.NoClassDefFoundError: Lcom/mysql/jdbc/Connection;
    Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.Connection from [Module \"deployment.UserManagment.war:main\" from Service Module Loader]"}}
20:26:56,667 INFO  [org.jboss.as.server] (ServerService Thread Pool -- 29) JBAS018559: Deployed "UserManagment.war" (runtime-name : "UserManagment.war")
20:26:56,671 INFO  [org.jboss.as.controller] (Controller Boot Thread) JBAS014774: Service status report
JBAS014777:   Services which failed to start:      service jboss.undertow.deployment.default-server.default-host./UserManagment: org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./UserManagment: Failed to start service

20:26:56,866 INFO  [org.jboss.as] (Controller Boot Thread) JBAS015961: Http management interface listening on http://127.0.0.1:10090/management
20:26:56,866 INFO  [org.jboss.as] (Controller Boot Thread) JBAS015951: Admin console listening on http://127.0.0.1:10090
20:26:56,867 ERROR [org.jboss.as] (Controller Boot Thread) JBAS015875: WildFly 8.0.0.Final "WildFly" started (with errors) in 5188ms - Started 257 of 314 services (2 services failed or missing dependencies, 90 services are lazy, passive or on-demand)
20:26:56,931 INFO  [org.hibernate.validator.internal.util.Version] (MSC service thread 1-2) HV000001: Hibernate Validator 5.0.3.Final
20:26:56,982 INFO  [org.jboss.as.server.deployment] (MSC service thread 1-6) JBAS015877: Stopped deployment UserManagment.war (runtime-name: UserManagment.war) in 81ms
20:26:57,176 INFO  [org.jboss.as.server] (DeploymentScanner-threads - 2) JBAS018558: Undeployed "UserManagment.war" (runtime-name: "UserManagment.war")
20:26:57,178 INFO  [org.jboss.as.controller] (DeploymentScanner-threads - 2) JBAS014774: Service status report
JBAS014775:    New missing/unsatisfied dependencies:
      service jboss.deployment.unit."UserManagment.war".component."com.sun.faces.config.ConfigureListener".START (missing) dependents: [service jboss.deployment.unit."UserManagment.war".deploymentCompleteService] 
      service jboss.deployment.unit."UserManagment.war".component."javax.faces.webapp.FacetTag".START (missing) dependents: [service jboss.deployment.unit."UserManagment.war".deploymentCompleteService] 
      service jboss.deployment.unit."UserManagment.war".component."javax.servlet.jsp.jstl.tlv.PermittedTaglibsTLV".START (missing) dependents: [service jboss.deployment.unit."UserManagment.war".deploymentCompleteService] 
      service jboss.deployment.unit."UserManagment.war".component."javax.servlet.jsp.jstl.tlv.ScriptFreeTLV".START (missing) dependents: [service jboss.deployment.unit."UserManagment.war".deploymentCompleteService] 
      service jboss.undertow.deployment.default-server.default-host./UserManagment (missing) dependents: [service jboss.deployment.unit."UserManagment.war".deploymentCompleteService] 
JBAS014777:   Services which failed to start:      service jboss.undertow.deployment.default-server.default-host./UserManagment

20:27:01,705 INFO  [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 2) JBAS015003: Found UserManagment.war in deployment directory. To trigger deployment create a file called UserManagment.war.dodeploy

PS：我使用eclipse，wildfly 8.0作为服务器，postman尝试url，我已经创建了mysql数据库。当我删除数据库连接文件和用户服务中的数据库代码块时，它再次工作，这就是为什么我确定问题出在数据库连接上。

以防万一你想知道我的目标是什么，我正在开发一个Android应用程序，它消耗了一个从数据库中获取数据的宁静的web服务！

感谢您帮助我！

Answer 1

当我们看到NoClassDefFoundError，ClassNotFoundException，NoSuchMethodException之类的错误时，这意味着JVM在没有找到它的情况下搜索了一个类/方法。

但是等等，我的项目编译得很好，为什么它找不到它们？!!!

要回答我必须解释运行时依赖性和编译时依赖性之间的区别。

当A使用B.jar时（在你的情况下A是你的项目而B.jar是mysql.jar）我们说A依赖于B（B是A的依赖），如果A不能编译没有B但可以在没有它的情况下运行我们说B是编译时依赖，通常IDE不会将这些库复制到最终结果（jar或war文件）。

当A不能在没有B的情况下运行时，我们说B是运行时依赖，通常IDE包括那些进入最终结果（jar或war文件）。

在您的情况下，mysql.jar是一个运行时依赖项，但我希望您将其配置为编译时依赖项，这就是您的项目编译但无法运行的原因。

为了解决这个问题，我们在IDE中正确配置它，对于eclipse我们这样做（假设你已经将mysql.jar添加到了库中）：

右键单击该项目。
在Build Path下选择Configure Build Path。
点击Deployment Assembly。
点击添加，会弹出一个对话框，选择Java Build Path Entries。
从那里选择mysql.jar

如果这些步骤开始如我所料，eclipse会将mysql.jar复制到WEB-INF/lib文件夹中，您的问题将会解决（我的eclipse版本是Neon，我希望这些说明适用于您的版本）。

一些建议：

学习使用构建工具，我建议使用gradle，因为我觉得它是构建java项目的现代方法，但其他人也很好（gradle用于android :)）
您可能希望使用JDBC的一些抽象，特别是ORM，虽然并非所有人都同意我仍然建议您看一看，它们有标准（即jpa和jdo）并且有许多符合标准的实现（像往常一样使用非标准扩展），java中最受欢迎的ORM是Hibernate（但这并不意味着它是最好的因为它的例外对于维护来说是可怕的）

我无法将restful连接到mysql数据库

1 个答案: