在karaf3中加入jpa

1、不使用karaf自己的jpa，也就是不要feature:install jpa

2、使用EclipseLink jpa

3、要使用 http://wiki.eclipse.org/Gemini/JPA提供的模块化支持，在osgi环境中使用EclipseLink作为jpa

4、在karaf的deploy目录中加入以下bundles：

（1）EclipseLink的bundles

javax.persistence_2.0.4.v201112161009.jar 

org.eclipse.persistence.antlr_3.2.0.v201206041011.jar

org.eclipse.persistence.asm_3.3.1.v201206041142.jar

org.eclipse.persistence.core_2.4.1.v20121003-ad44345.jar

org.eclipse.persistence.jpa.jpql_2.0.1.v20121003-ad44345.jar

org.eclipse.persistence.jpa_2.4.1.v20121003-ad44345.jar

（2） Gemini/JPA的bundles

org.eclipse.gemini.jpa-1.1.0.RELEASE.jar

在这里下载： Gemini JPA Home

（3）从 http://www.osgi.org/Download/Release4V42下载的

osgi.enterprise.jar

（4）数据库的jdbc驱动器

mysql-connector-java-5.1.24-bin.jar

5、编写持久化单元bundle

在这个bundle中包含三部分：

（1）实体定义

package  dwpaas.console;

import  javax.persistence.Entity;
import  javax.persistence.GeneratedValue;
import  javax.persistence.Id;

@Entity
public class DwpaasUser {
@Id
@GeneratedValue
private Integer id;
private String username;
private String name;
private String password;
public Integer getId() {
returnid;
}
publicvoid setId(Integer id) {
this.id = id;
}
public String getUsername() {
returnusername;
}
publicvoid setUsername(String username) {
this.username = username;
}
public String getName() {
returnname;
}
publicvoid setName(String name) {
this.name = name;
}
public String getPassword() {
returnpassword;
}
publicvoid setPassword(String password) {
this.password = password;
}

}

（2）持久化单元定义：persistence.xml，该文件放在META-INF目录下

xml version="1.0"encoding="UTF-8"?>
<persistenceversion="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-unitname="dwmc"transaction-type="RESOURCE_LOCAL"]]>
<provider]]>org.eclipse.persistence.jpa.PersistenceProviderprovider]]>
<class]]>dwpaas.console.DwpaasUserclass]]>
<properties]]>
<propertyname="javax.persistence.jdbc.url"
value="jdbc:mysql://localhost:3306/dwmc?useUnicode=true&characterEncoding=UTF-8"/>
<propertyname="javax.persistence.jdbc.user"value="dwmc"/>
<propertyname="javax.persistence.jdbc.password"value="dwmc6309"/>
<propertyname="javax.persistence.jdbc.driver"value="com.mysql.jdbc.Driver"/>
<propertyname="eclipselink.logging.level"value="OFF"/>
<propertyname="eclipselink.orm.throw.exceptions"value="true"/>
<propertyname="eclipselink.ddl-generation"value="drop-and-create-tables"/>
            <propertyname="eclipselink.ddl-generation.output-mode"value="database"/>
properties]]>
persistence-unit]]>
persistence]]>

（3）在bundle的描述文件中增加：

Meta-Persistence : META-INF/persistence.xml

其完整的内容如下：

Manifest-Version : 1.0
Bundle-ManifestVersion : 2
Bundle-Name : Pu
Bundle-SymbolicName : dwpaas.console.pu
Bundle-Version : 1.0.0.qualifier
Bundle-Vendor : Dareway
Bundle-RequiredExecutionEnvironment : JavaSE-1.6
Meta-Persistence : META-INF/persistence.xml
Import-Package : com.mysql.jdbc; version ="5.1.24",
 javax.persistence; version ="2.0.4"

部署该持久化单元bundle之后，就会在osgi环境中自动注册emf服务。

6、 EntityManagerFactory服务

Property Name	Property Value
osgi.unit.name	Name of the persistence unit
osgi.unit.version	Bundle version of the persistence bundle
osgi.unit.provider	Class name of assigned provider
osgi.managed.bundles	Bundle id of the persistence bundle

利用下述代码从osgi环境中获得emf服务：

public static EntityManagerFactory lookupEMF(String unitName) {
ServiceReference[] refs = null;
try {
refs = context.getServiceReferences(EntityManagerFactory.class
.getName(), String.format("(%s=%s)",
EntityManagerFactoryBuilder.JPA_UNIT_NAME, unitName));
} catch (InvalidSyntaxException isEx) {
thrownew RuntimeException("Filter error", isEx);
}
return (refs == null) ? null : (EntityManagerFactory)context
.getService(refs[0]);
 

}

该方法是在bundle的Activator中实现的，其中的context就是osgi的 BundleContext。

使用emf访问数据库：

EntityManagerFactory emf = lookupEMF( "dwmc" );
if (emf !=null){
System.out.println("get emf successful.");
EntityManager em = emf.createEntityManager();
}else{
System.out.println("get emf not successful.");
 

}

7、在karaf的console使用下述命令可以看到：

karaf@root()> bundle:list

START LEVEL 100 , List Threshold: 50

   ID   State         Level Name

[  91] [  Resolved] [   80] XBean-Finder-Fragment (3.0.0.M3), Hosts: 92

[ 116] [    Active] [   80] Java Persistence API 2.0 (2.0.4.v201112161009)

[ 117] [    Active] [   80] EclipseLink JPA (2.4.1.v20121003-ad44345)

[ 118] [    Active] [   80] EclipseLink Core (2.4.1.v20121003-ad44345)

[ 119] [    Active] [   80] EclipseLink ANTLR (3.2.0.v201206041011)

[ 120] [    Active] [   80] EclipseLink ASM (3.3.1.v201206041142)

[ 121] [    Active] [   80] osgi.enterprise (4.2.0.201003190513)

[ 122] [    Active] [   80] EclipseLink Hermes Parser (2.0.1.v20121003-ad44345)

[ 123] [    Active] [   80] Sun Microsystems' JDBC Driver for MySQL (5.1.24)

[ 124] [    Active] [   80] Pu (1.0.0.1)

[ 125] [    Active] [   80] Emf (1.0.0.1)

[ 126] [    Active] [   80] Gemini JPA (1.1.0.RELEASE)