JPA Vendor Adapters

// PostgreSQL
vendorAdapter.setDatabase(Database.POSTGRESQL);
vendorAdapter.setDatabasePlatform("org.hibernate.dialect.PostgreSQLDialect");

// MySQL
vendorAdapter.setDatabase(Database.MYSQL);
vendorAdapter.setDatabasePlatform("org.hibernate.dialect.MySQL8Dialect");

// Oracle
vendorAdapter.setDatabase(Database.ORACLE);
vendorAdapter.setDatabasePlatform("org.hibernate.dialect.Oracle12cDialect");

// SQL Server
vendorAdapter.setDatabase(Database.SQL_SERVER);
vendorAdapter.setDatabasePlatform("org.hibernate.dialect.SQLServerDialect");

// H2 (for testing)
vendorAdapter.setDatabase(Database.H2);
vendorAdapter.setDatabasePlatform("org.hibernate.dialect.H2Dialect");

import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.Database;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;

@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
    LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
    em.setDataSource(dataSource);
    em.setPackagesToScan("com.example.domain");

    HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
    vendorAdapter.setDatabase(Database.POSTGRESQL);
    vendorAdapter.setGenerateDdl(false);  // false in production
    vendorAdapter.setShowSql(false);      // false in production
    em.setJpaVendorAdapter(vendorAdapter);

    return em;
}

@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
    LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
    em.setDataSource(dataSource);
    em.setPackagesToScan("com.example.domain");

    HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
    vendorAdapter.setDatabase(Database.MYSQL);
    vendorAdapter.setDatabasePlatform("org.hibernate.dialect.MySQL8Dialect");
    vendorAdapter.setGenerateDdl(false);
    vendorAdapter.setShowSql(true);
    vendorAdapter.setPrepareConnection(true);  // Optimize read-only transactions
    em.setJpaVendorAdapter(vendorAdapter);

    return em;
}

class HibernateJpaVendorAdapter {

    // Constructor
    HibernateJpaVendorAdapter();

    // Connection preparation for read-only transactions
    void setPrepareConnection(boolean prepareConnection);

    // Inherited from AbstractJpaVendorAdapter
    void setDatabase(Database database);
    Database getDatabase();

    void setDatabasePlatform(String databasePlatform);
    String getDatabasePlatform();

    void setGenerateDdl(boolean generateDdl);
    boolean isGenerateDdl();

    void setShowSql(boolean showSql);
    boolean isShowSql();

    // Access provider and dialect
    PersistenceProvider getPersistenceProvider();
    String getPersistenceProviderRootPackage();
    Map<String, Object> getJpaPropertyMap(PersistenceUnitInfo pui);
    Map<String, Object> getJpaPropertyMap();
    HibernateJpaDialect getJpaDialect();
    Class<? extends EntityManagerFactory> getEntityManagerFactoryInterface();
    Class<? extends EntityManager> getEntityManagerInterface();
}

import org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter;

@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
    LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
    em.setDataSource(dataSource);
    em.setPackagesToScan("com.example.domain");

    EclipseLinkJpaVendorAdapter vendorAdapter = new EclipseLinkJpaVendorAdapter();
    vendorAdapter.setDatabase(Database.POSTGRESQL);
    vendorAdapter.setGenerateDdl(true);
    vendorAdapter.setShowSql(true);
    em.setJpaVendorAdapter(vendorAdapter);

    return em;
}

class EclipseLinkJpaVendorAdapter {

    // Inherited from AbstractJpaVendorAdapter
    void setDatabase(Database database);
    void setDatabasePlatform(String databasePlatform);
    void setGenerateDdl(boolean generateDdl);
    void setShowSql(boolean showSql);

    // Access provider and dialect
    PersistenceProvider getPersistenceProvider();
    Map<String, Object> getJpaPropertyMap();
    EclipseLinkJpaDialect getJpaDialect();
    Class<? extends EntityManager> getEntityManagerInterface();
}

enum Database {
    DEFAULT,     // Use default detection
    DB2,         // IBM DB2
    DERBY,       // Apache Derby
    H2,          // H2 Database
    HANA,        // SAP HANA
    HSQL,        // HyperSQL
    INFORMIX,    // IBM Informix
    MYSQL,       // MySQL/MariaDB
    ORACLE,      // Oracle Database
    POSTGRESQL,  // PostgreSQL
    SQL_SERVER,  // Microsoft SQL Server
    SYBASE       // SAP Sybase
}

import org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator;
import org.springframework.jdbc.support.SQLExceptionTranslator;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.vendor.HibernateJpaDialect;

@Bean
public JpaTransactionManager transactionManager(
        EntityManagerFactory entityManagerFactory,
        DataSource dataSource) {
    JpaTransactionManager transactionManager = new JpaTransactionManager();
    transactionManager.setEntityManagerFactory(entityManagerFactory);

    // Configure Hibernate-specific JPA dialect
    HibernateJpaDialect jpaDialect = new HibernateJpaDialect();
    jpaDialect.setPrepareConnection(true);

    // Custom JDBC exception translator
    SQLExceptionTranslator exceptionTranslator =
        new SQLErrorCodeSQLExceptionTranslator(dataSource);
    jpaDialect.setJdbcExceptionTranslator(exceptionTranslator);

    transactionManager.setJpaDialect(jpaDialect);

    return transactionManager;
}

class HibernateJpaDialect {

    // Connection preparation
    void setPrepareConnection(boolean prepareConnection);

    // JDBC exception translator
    void setJdbcExceptionTranslator(SQLExceptionTranslator translator);

    // Inherited from DefaultJpaDialect
    Object beginTransaction(EntityManager em, TransactionDefinition def);
    Object prepareTransaction(EntityManager em, boolean readOnly, String name);
    void cleanupTransaction(Object transactionData);
    ConnectionHandle getJdbcConnection(EntityManager em, boolean readOnly);
    DataAccessException translateExceptionIfPossible(RuntimeException ex);
}

@Configuration
@EnableTransactionManagement
public class JpaConfig {

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource);
        em.setPackagesToScan("com.example.domain");

        // Configure Hibernate vendor adapter
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setDatabase(Database.POSTGRESQL);
        vendorAdapter.setGenerateDdl(false);
        vendorAdapter.setShowSql(true);
        vendorAdapter.setPrepareConnection(true);
        em.setJpaVendorAdapter(vendorAdapter);

        // Additional JPA properties
        Map<String, Object> properties = new HashMap<>();
        properties.put("hibernate.format_sql", "true");
        properties.put("hibernate.use_sql_comments", "true");
        properties.put("hibernate.jdbc.batch_size", "20");
        properties.put("hibernate.cache.use_second_level_cache", "true");
        em.setJpaPropertyMap(properties);

        return em;
    }

    @Bean
    public PlatformTransactionManager transactionManager(
            EntityManagerFactory entityManagerFactory,
            DataSource dataSource) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(entityManagerFactory);

        // Configure Hibernate JPA dialect
        HibernateJpaDialect jpaDialect = new HibernateJpaDialect();
        jpaDialect.setPrepareConnection(true);
        transactionManager.setJpaDialect(jpaDialect);

        return transactionManager;
    }
}