SAP HANA Cloud 如何支持多个数据库？

Question

我有一个场景，我需要在 SAP HANA 云平台（目标运行时是 JAVA Web）中部署我的 vaadin 应用程序（与多个数据库（2 个持久性单元）一起工作，其中运行时是 tomcat 7）。

我之前的数据库连接是通过以下方式使用 eclipselink 与 MYSQL 进行的

private EntityManager getEntityManager(String dbName) {
        EntityManagerFactory emf = null;
        Map<String, String> properties = new HashMap<String, String>();
        if (dbName.toLowerCase().contains("master"))
            properties.put(
                    PersistenceUnitProperties.ECLIPSELINK_PERSISTENCE_XML,
                    "/META-INF/persistence.xml");
        else
            properties.put(
                    PersistenceUnitProperties.ECLIPSELINK_PERSISTENCE_XML,
                    "/META-INF/persistenceYear.xml");// +dbName.substring(dbName.length()-4)+".xml");
        properties.put("javax.persistence.jdbc.driver", getDriver());
        properties
                .put("javax.persistence.jdbc.url",
                        getUrl()
                                + dbName
                                + "?zeroDateTimeBehavior=convertToNull&amp;useUnicode=yes&amp;characterEncoding=utf-8;charset=utf8;characterSetResults=utf8");// &amp;characterSetResults=utf8");
        // properties.put("javax.persistence.jdbc.url",
        // getUrl()+dbName+"?useUnicode=yes&amp;characterEncoding=UTF-8;characterSetResults=utf8");
        properties.put("javax.persistence.jdbc.user", getUserName());
        properties.put("javax.persistence.jdbc.password", getPassword());
        properties.put(PersistenceUnitProperties.TABLE_CREATION_SUFFIX,
                "engine=InnoDB DEFAULT CHARSET=utf8");

        properties.put(PersistenceUnitProperties.DDL_GENERATION,
                PersistenceUnitProperties.CREATE_OR_EXTEND);
        properties.put(PersistenceUnitProperties.DDL_GENERATION_MODE,
                PersistenceUnitProperties.DDL_DATABASE_GENERATION);
        // properties.put(PersistenceUnitProperties.CREATE_JDBC_DDL_FILE,"create.sql");
        // properties.put(PersistenceUnitProperties.APP_LOCATION,
        // ServerFolderPathConstants.PROPERTYFILES);

        // Configure Session Customizer which will pipe sql file to db before
        // DDL Generation runs
        // properties.put(PersistenceUnitProperties.SESSION_CUSTOMIZER,
        // "in.calico.finbook.config.common.ImportSQL");
        // properties.put("import.sql.file",ServerFolderPathConstants.PROPERTYFILES+"create.sql");
        try {
            /*
             * emf = Persistence.createEntityManagerFactory("finbook",
             * properties);
             */
            emf = Persistence.createEntityManagerFactory(getUnit(), properties);
        } catch (Exception e) {
            // System.out.println(e.getMessage());
            e.printStackTrace();
        }
        return emf.createEntityManager();
    }

上述方法有助于连接数据库（MYSQL）并返回实体管理器。

我的应用程序需要使用相同的方法，该方法将部署在 SAP HANA CLOUD 中。我想知道如何获得实体管理器（多个数据库）以及如何创建我需要连接的架构？

请帮帮我。

Answer 1

在阅读了 sap hana 云平台的完整文档后，我明白了，我在 sap hana cockpit 的 java 应用程序部分部署了我的 war 文件。通过 JPA 2.0，我连接到 SAP DB (source to create DB and binding is) 并在代码下方获取实体管理器对象有很大帮助

    import javax.sql.DataSource;
    import javax.annotation.Resource;
    import javax.annotation.Resources;
    import javax.naming.InitialContext;
    import javax.naming.NamingException;
    import javax.persistence.EntityManager;
    import javax.persistence.EntityManagerFactory;
    import javax.persistence.Persistence;
    import javax.servlet.annotation.WebServlet;

{
    DataSource ds =null;
                          EntityManagerFactory emf;
                        InitialContext ctx = null;
                            try {
                                ctx = new InitialContext();
                            } catch (NamingException e) {
                                e.printStackTrace();
                            }
                          try {
        //Note: jdbc/fbk is data source name which we'll give at binding database, by default it will be as "<default>" edit that to jdbc/fbk or else anything
                                ds = (DataSource) ctx.lookup("java:comp/env/jdbc/fbk");
                            } catch (NamingException e) {
                                e.printStackTrace();
                            }

                          @SuppressWarnings("rawtypes")
                            Map properties = new HashMap();
                          properties.put(PersistenceUnitProperties.JTA_DATASOURCE, ds);
                        properties.put(PersistenceUnitProperties.DDL_GENERATION,
                                PersistenceUnitProperties.CREATE_OR_EXTEND);
                        properties.put(PersistenceUnitProperties.DDL_GENERATION_MODE,
                                PersistenceUnitProperties.DDL_DATABASE_GENERATION);
                          emf = Persistence.createEntityManagerFactory("pu", properties);
                          EntityManager em = emf.createEntityManager();
return em;
}

persistence.xml 代码为：

<?xml version="1.0" encoding="UTF-8"?>
<persistence 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"
    version="2.0">

     <persistence-unit name="pu" transaction-type="JTA">
     <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
     <class>Vaadin_Sample.hell.FunctionKey</class>

         <properties>
            </properties>
       </persistence-unit>
    </persistence>

资源映射是在以下注释的帮助下完成的：

 @WebServlet(urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true)
    @VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
    @Resource(name="jdbc/fbk",type=DataSource.class)
    public static class MyUIServlet extends VaadinServlet {
    }

注意：以上所有流程仅由 COCKPIT 的试用账户完成。