OpenJPA 输出 SQL 日志和使用连接池的方法

How do I see the SQL that OpenJPA is executing?

OpenJPA provides configurable channel-based logging, as described in the chapter on Logging. The simplest example of enabling verbose logging is by using the following property in your persistence.xml file:

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    version="1.0">
    <persistence-unit name="example-logging" transaction-type="RESOURCE_LOCAL">
        <properties>
            <property name="openjpa.Log" value="SQL=TRACE"/>
        </properties>
    </persistence-unit>
</persistence> 

How do I enable connection pooling in OpenJPA?

OpenJPA doesn't include any built-in connection pool, but you can use any third-party connection pool that is configurable via the JDBC DataSource API (which most are). The following persistence.xml example shows how to use OpenJPA with a Apache Derby database and the Apache DBCP connection pool:

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    version="1.0">
    <persistence-unit name="example-derby" transaction-type="RESOURCE_LOCAL">
        <properties>
            <property name="openjpa.ConnectionProperties" 
                value="DriverClassName=org.apache.derby.jdbc.ClientDriver,
                  Url=jdbc:derby://localhost:1527/database, 
                  MaxActive=100, 
                  MaxWait=10000, 
                  TestOnBorrow=true, 
                  Username=user, 
                  Password=secret"/>
            <property name="openjpa.ConnectionDriverName" 
                value="org.apache.commons.dbcp.BasicDataSource"/>
        </properties>
    </persistence-unit>
</persistence> 

See the documentation on Using a Third-Party DataSource for further details.