Java JPA：从属性创建EntityManagerFactory

我在一个JAR项目中使用JPA，并使用persistence.xml来设置我的EntityManager

但是，由于persistence.xml在构建之后位于JAR中，因此用户在构建之后更改设置非常复杂。因此，我正在寻找一种解决方案，可以在运行时加载的propertyfile上配置连接

我在网上发现了这个解决方案：

Map properties = new HashMap();

// Configure the internal EclipseLink connection pool
properties.put(JDBC_DRIVER, "oracle.jdbc.OracleDriver");
properties.put(JDBC_URL, "jdbc:oracle:thin:@localhost:1521:ORCL");
properties.put(JDBC_USER, "user-name");
properties.put(JDBC_PASSWORD, "password");

Persistence.createEntityManagerFactory("unit-name", properties);

这是我一直在寻找的解决方案，但我缺少一件事：在我的persistence.xml中，我还声明了映射文件上的模式名称：

persistence.xml：

<persistence version="2.0" ...>
  <persistence-unit name="jpa" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>...</class>
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <properties>
      <property name="javax.persistence.jdbc.url" value="..."/>
      <property name="javax.persistence.jdbc.password" value="..."/>
      <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver"/>
      <property name="javax.persistence.jdbc.user" value="..."/>
    </properties>
    <mapping-file>META-INF/orm.xml</mapping-file>
  </persistence-unit>
</persistence>

org.eclipse.persistence.jpa.PersistenceProvider
...
真的
META-INF/orm.xml

orm.xml：

<entity-mappings ...>
 <persistence-unit-metadata>
  <persistence-unit-defaults>
   <schema>SCHEMA_NAME</schema>
  </persistence-unit-defaults>
 </persistence-unit-metadata>
</entity-mappings>

模式名称

所以我的问题基本上是：是否有一个属性可以用来在运行时设置模式，就像我对其他属性所做的那样

还是有更好的解决方案

---

提前谢谢

我不知道这是否是一个更好的解决方案，但您可以使用所需的模式注释您的JPA实体

@Entity
@Table(name = "Foo", schema = "Bar")

---

切换到java配置。然后，您可以通过自动关联环境轻松地插入属性值

这个例子非常基本。但一般来说，如果您知道如何进行xml配置，您可以直接将其映射到Java配置

contextConfig.java

/**
 * Spring Context configuration.
 */
@ComponentScan(basePackages = { "com.example" })
@PropertySource({ "classpath:common.properties" })
@Configuration
@Import(JpaConfig.class)
public class ContextConfig extends WebMvcConfigurerAdapter {
    /**
     * This bean is needed because Spring when you use xml config to load property files the bean is automatically
     * created... when you use @PropertySource then not so much
     * @return new bean
     */
    @Bean
    public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
        return new PropertySourcesPlaceholderConfigurer();
    }
}

@Configuration
@EnableJpaRepositories("com.example.repository")
public class JpaConfig {

    @Autowired
    private Environment env;

    /**
     * Create the fooDataSource Bean.
     * @return fooDataSource Bean
     */
    @Bean
    public BasicDataSource fooDataSource() {

        BasicDataSource basicDataSource = new BasicDataSource();
        basicDataSource.setDriverClassName(env.getProperty("cfg_foo.driver.name"));
        basicDataSource.setUrl(env.getProperty("cfg_foo.jdbc.url"));
        basicDataSource.setUsername(env.getProperty("cfg_foo.username"));
        basicDataSource.setPassword(env.getProperty("cfg_foo.password"));
        basicDataSource.setPoolPreparedStatements(Boolean.valueOf(env.getProperty("cfg_foo.poolPreparedStatements")));
        basicDataSource.setInitialSize(Integer.valueOf(env.getProperty("cfg_foo.poolInitialSize")));
        basicDataSource.setMaxActive(Integer.valueOf(env.getProperty("cfg_foo.poolMaxActive")));
        basicDataSource.setMaxIdle(Integer.valueOf(env.getProperty("cfg_foo.poolMaxIdle")));
        basicDataSource.setValidationQuery("SELECT '1'");

        return basicDataSource;
    }

    /**
     * Create the hibernateJpaVendorAdapter Bean.
     * @return hibernateJpaVendorAdapter Bean
     */
    @Bean
    public HibernateJpaVendorAdapter hibernateJpaVendorAdapter() {

        HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
        adapter.setDatabasePlatform("org.hibernate.dialect.MySQLDialect");
        adapter.setShowSql(Boolean.valueOf(env.getProperty("show.sql")));
        adapter.setGenerateDdl(Boolean.valueOf(env.getProperty("format.sql")));

        return adapter;
    }

    /**
     * Create the entityManagerFactory Bean.
     * @return entityManagerFactory Bean
     */
    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

        LocalContainerEntityManagerFactoryBean entityManagerFactory = new LocalContainerEntityManagerFactoryBean();
        entityManagerFactory.setPersistenceUnitName("foo");
        entityManagerFactory.setDataSource(fooDataSource());
        entityManagerFactory.setJpaVendorAdapter(hibernateJpaVendorAdapter());
        entityManagerFactory.setPackagesToScan("com.example.repository");

        return entityManagerFactory;
    }

}

jpaConfig.java

/**
 * Spring Context configuration.
 */
@ComponentScan(basePackages = { "com.example" })
@PropertySource({ "classpath:common.properties" })
@Configuration
@Import(JpaConfig.class)
public class ContextConfig extends WebMvcConfigurerAdapter {
    /**
     * This bean is needed because Spring when you use xml config to load property files the bean is automatically
     * created... when you use @PropertySource then not so much
     * @return new bean
     */
    @Bean
    public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
        return new PropertySourcesPlaceholderConfigurer();
    }
}

@Configuration
@EnableJpaRepositories("com.example.repository")
public class JpaConfig {

    @Autowired
    private Environment env;

    /**
     * Create the fooDataSource Bean.
     * @return fooDataSource Bean
     */
    @Bean
    public BasicDataSource fooDataSource() {

        BasicDataSource basicDataSource = new BasicDataSource();
        basicDataSource.setDriverClassName(env.getProperty("cfg_foo.driver.name"));
        basicDataSource.setUrl(env.getProperty("cfg_foo.jdbc.url"));
        basicDataSource.setUsername(env.getProperty("cfg_foo.username"));
        basicDataSource.setPassword(env.getProperty("cfg_foo.password"));
        basicDataSource.setPoolPreparedStatements(Boolean.valueOf(env.getProperty("cfg_foo.poolPreparedStatements")));
        basicDataSource.setInitialSize(Integer.valueOf(env.getProperty("cfg_foo.poolInitialSize")));
        basicDataSource.setMaxActive(Integer.valueOf(env.getProperty("cfg_foo.poolMaxActive")));
        basicDataSource.setMaxIdle(Integer.valueOf(env.getProperty("cfg_foo.poolMaxIdle")));
        basicDataSource.setValidationQuery("SELECT '1'");

        return basicDataSource;
    }

    /**
     * Create the hibernateJpaVendorAdapter Bean.
     * @return hibernateJpaVendorAdapter Bean
     */
    @Bean
    public HibernateJpaVendorAdapter hibernateJpaVendorAdapter() {

        HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
        adapter.setDatabasePlatform("org.hibernate.dialect.MySQLDialect");
        adapter.setShowSql(Boolean.valueOf(env.getProperty("show.sql")));
        adapter.setGenerateDdl(Boolean.valueOf(env.getProperty("format.sql")));

        return adapter;
    }

    /**
     * Create the entityManagerFactory Bean.
     * @return entityManagerFactory Bean
     */
    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

        LocalContainerEntityManagerFactoryBean entityManagerFactory = new LocalContainerEntityManagerFactoryBean();
        entityManagerFactory.setPersistenceUnitName("foo");
        entityManagerFactory.setDataSource(fooDataSource());
        entityManagerFactory.setJpaVendorAdapter(hibernateJpaVendorAdapter());
        entityManagerFactory.setPackagesToScan("com.example.repository");

        return entityManagerFactory;
    }

}

---

META-INF/orm.xml

是默认名称，如果文件存在，无论是否在持久化单元中指定，都将使用该文件。如果

persistence.xml

中的映射文件有其他名称，则不使用默认名称

---

要使用多个不兼容的数据库提供程序，如SQL Server和Oracle，可以在

persistence.xml

中有多个持久化单元，并在运行时选择合适的单元。如果映射文件使用非默认名称命名，则每个单元可以有自己的映射文件，也可以根本没有映射文件。

使用此类PersistenceUnitProperties作为名称

see链接

房地产实例

javax.persistence.jdbc.driver=org.sqlite.JDBC
eclipselink.ddl-generation=create-tables
#eclipselink.ddl-generation=none
javax.persistence.jdbc.url=jdbc:sqlite:domo.db

持久性示例（Persistence.xml）

提供程序的Eclipse依赖性示例

    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>org.eclipse.persistence.jpa</artifactId>
        <version>2.7.4</version>
    </dependency>

org.eclipse.persistence
org.eclipse.persistence.jpa
2.7.4

对模式进行硬编码，这样用户就根本无法更改模式了吗？确实如此。避免这种硬编码。我在答案中添加了一个非常基本的示例。希望能有所帮助：）谢谢这个例子，现在你所说的更清楚了。但是我们在这个项目中没有使用Spring，我看不到您在哪里配置模式？（我错过了什么吗？）哦。。。道歉。我不知道没有弹簧怎么做