Java 如何在GWT项目中使用JPA（Hibernate）连接到MySQL数据库？
我可以在示例Java项目中使用JPA。这就是它的样子： 我使用MySQL数据库。我用Hibernate4.3.5连接到它 项目树： 我导入了这些.jar文件： （它包含Hibernate 4.3.5.jar文件和mysql-connector-java-5.1.29-bin.jar文件） 这是persistence.xml文件：Java 如何在GWT项目中使用JPA（Hibernate）连接到MySQL数据库？,java,mysql,hibernate,gwt,jpa,Java,Mysql,Hibernate,Gwt,Jpa,我可以在示例Java项目中使用JPA。这就是它的样子： 我使用MySQL数据库。我用Hibernate4.3.5连接到它 项目树： 我导入了这些.jar文件： （它包含Hibernate 4.3.5.jar文件和mysql-connector-java-5.1.29-bin.jar文件） 这是persistence.xml文件： <?xml version="1.0" encoding="UTF-8"?> <persistence version="2.0" xm
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="DB" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.show_sql" value="true" />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://127.0.0.1:3306/mintaalkalmazas2"/>
<property name="javax.persistence.jdbc.user" value="root" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
</properties>
</persistence-unit>
</persistence>
...
@Entity
@Table(name="kerdes")
public class Kerdes {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;
@Column
private int feladatlapID;
@Column
private String kerdes;
@Column
private int tipus;
@Column
private int sorszam;
@Column
private String valasz;
...
static EntityManagerFactory emf = Persistence.createEntityManagerFactory("DB");
static EntityManager em = emf.createEntityManager();
public static void main(String[] args) {
try {
em.getTransaction().begin();
insert();
select();
update();
delete();
em.getTransaction().commit();
}
catch (Exception e) {
em.getTransaction().rollback();
e.printStackTrace();
}
finally{
emf.close();
}
System.out.println("It is over");
}
...
static EntityManagerFactory emf = Persistence.createEntityManagerFactory("DB");
static EntityManager em = emf.createEntityManager();
public GreetingServiceImpl() {
try {
em.getTransaction().begin();
insert();
select();
update();
delete();
em.getTransaction().commit();
}
catch (Exception e) {
em.getTransaction().rollback();
e.printStackTrace();
}
finally{
emf.close();
}
System.out.println("It is over");
}
...
我试图在GWT应用程序中实现同样的功能。我会连接到同一个数据库，我想做同样的事情。我用示例代码生成了项目，并将我的方法添加到服务器 这是项目树：
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="DB" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.show_sql" value="true" />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://127.0.0.1:3306/mintaalkalmazas2"/>
<property name="javax.persistence.jdbc.user" value="root" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
</properties>
</persistence-unit>
</persistence>
...
@Entity
@Table(name="kerdes")
public class Kerdes {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;
@Column
private int feladatlapID;
@Column
private String kerdes;
@Column
private int tipus;
@Column
private int sorszam;
@Column
private String valasz;
...
static EntityManagerFactory emf = Persistence.createEntityManagerFactory("DB");
static EntityManager em = emf.createEntityManager();
public static void main(String[] args) {
try {
em.getTransaction().begin();
insert();
select();
update();
delete();
em.getTransaction().commit();
}
catch (Exception e) {
em.getTransaction().rollback();
e.printStackTrace();
}
finally{
emf.close();
}
System.out.println("It is over");
}
...
static EntityManagerFactory emf = Persistence.createEntityManagerFactory("DB");
static EntityManager em = emf.createEntityManager();
public GreetingServiceImpl() {
try {
em.getTransaction().begin();
insert();
select();
update();
delete();
em.getTransaction().commit();
}
catch (Exception e) {
em.getTransaction().rollback();
e.printStackTrace();
}
finally{
emf.close();
}
System.out.println("It is over");
}
...
WARNING: Error for /gwtjpa/greet
java.lang.ExceptionInInitializerError
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:153)
at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:428)
at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:339)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:127)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:98)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:490)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: javax.persistence.PersistenceException: No persistence providers available for "DB" after trying the following discovered implementations: org.datanucleus.api.jpa.PersistenceProviderImpl
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:180)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:70)
at com.gwtjpa.server.GreetingServiceImpl.<clinit>(GreetingServiceImpl.java:24)
... 43 more
aug. 08, 2014 9:02:47 DU com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: Nested in java.lang.ExceptionInInitializerError:
javax.persistence.PersistenceException: No persistence providers available for "DB" after trying the following discovered implementations: org.datanucleus.api.jpa.PersistenceProviderImpl
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:180)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:70)
at com.gwtjpa.server.GreetingServiceImpl.<clinit>(GreetingServiceImpl.java:24)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:153)
at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:428)
at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:339)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:127)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:98)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:490)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
警告/gwtjpa/greet的错误
java.lang.ExceptionInInitializeError
位于sun.reflect.NativeConstructorAccessorImpl.newInstance0（本机方法）
位于sun.reflect.NativeConstructorAccessorImpl.newInstance（未知源）
位于sun.reflect.delegatingConstructor或AccessorImpl.newInstance（未知源）
位于java.lang.reflect.Constructor.newInstance（未知源）
位于java.lang.Class.newInstance（未知源）
位于org.mortbay.jetty.servlet.Holder.newInstance（Holder.java:153）
位于org.mortbay.jetty.servlet.ServletHolder.initServlet（ServletHolder.java:428）
位于org.mortbay.jetty.servlet.ServletHolder.getServlet（ServletHolder.java:339）
位于org.mortbay.jetty.servlet.ServletHolder.handle（ServletHolder.java:487）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1166）
位于com.google.appengine.api.socket.dev.DevSocketFilter.doFilter（DevSocketFilter.java:74）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
位于com.google.appengine.tools.development.ResponseWriterFilter.doFilter（responseWriterFilter.java:127）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
位于com.google.appengine.tools.development.headerficationfilter.doFilter（headerficationfilter.java:34）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
在com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter上（ServeBlobFilter.java:63）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
位于com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter（TransactionCleanupFilter.java:43）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
位于com.google.appengine.tools.development.StaticFileFilter.doFilter（StaticFileFilter.java:125）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
在com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest（DevAppServerModulesFilter.java:366）
位于com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest（DevAppServerModulesFilter.java:349）
位于com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter（DevAppServerModulesFilter.java:116）
位于org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter（ServletHandler.java:1157）
位于org.mortbay.jetty.servlet.ServletHandler.handle（ServletHandler.java:388）
位于org.mortbay.jetty.security.SecurityHandler.handle（SecurityHandler.java:216）
位于org.mortbay.jetty.servlet.SessionHandler.handle（SessionHandler.java:182）
位于org.mortbay.jetty.handler.ContextHandler.handle（ContextHandler.java:765）
位于org.mortbay.jetty.webapp.WebAppContext.handle（WebAppContext.java:418）
位于com.google.appengine.tools.development.devappengineewebappcontext.handle（devappengineewebappcontext.java:98）
位于org.mortbay.jetty.handler.HandlerWrapper.handle（HandlerWrapper.java:152）
位于com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle（JettyContainerService.java:490）
位于org.mortbay.jetty.handler.HandlerWrapper.handle（HandlerWrapper.java:152）
位于org.mortbay.jetty.Server.handle（Server.java:326）
位于org.mortbay.jetty.HttpConnection.handleRequest（HttpConnection.java:542）
位于org.mortbay.jetty.HttpConnection$RequestHandler.content（HttpConnection.java:938）
位于org.mortbay.jetty.HttpParser.parseNext（HttpParser.java:755）
位于org.mortbay.jetty.HttpParser.parseAvailable（HttpParser.java:218）
位于org.mortbay.jetty.HttpConnection.handle（HttpConnection.java:404）
位于org.mortbay.io.nio.SelectChannelEndPoint.run（SelectChannelEndPoint.java:409）
位于org.mortbay.thread.QueuedThreadPool$PoolThread.run（QueuedThreadPool.java:582）
原因：javax.persistence.PersistenceException:在尝试以下发现的实现后，“DB”没有可用的持久性提供程序：org.datanucleus.api.jpa.PersistenceProviderImpl
位于javax.persistence.persistence.createEntityManagerFactory（persistence.java:180）
位于javax.persistence.persistence.createEntityManagerFactory（persistence.java:70）
位于com.gwtjpa.server.greetingserviceinpl.（greetingserviceinpl.java:24）
... 43多
2014年8月8日9:02:47 DU com.google.apphosting.utils.jetty.JettyLogger警告
警告：嵌套在java.lang.ExceptionInInitializeError中：
javax.persistence.PersistenceException：在尝试以下发现的实现后，“DB”没有可用的持久性提供程序：org.data