非jta数据源如何工作？是否有必要在persistence .xml本身中提供持久性单元？

Question

This is

• What is the difference between non-jta-datasource and jta-datasource?

In the below code i didnt specified the persistence unit instead i have used non-jta- datasource how this working?is it possible to do like this?

<?xml version="1.0" encoding="UTF-8"?>
    <persistence version="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-unit name="bookPU" transaction-type="RESOURCE_LOCAL"> 
            <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider> 
             <non-jta-data-source>java:/comp/env/jdbc/bookDS</non-jta-data-source>
            <class>com.admin.Author</class> 
            <class>com.admin.Book</class> 

            <exclude-unlisted-classes>false</exclude-unlisted-classes>
    </persistence-unit> 
    </persistence>

Answer 1

Your persistance.xml does contain persistance unit named bookPU. The first xml you have posted contains non jat datasource and second xml contains jta datasource. Normally non JTA datasource would be used in unit test cases where other resource like JMS need not fall under a single transaction. However in cases of actual application we use JTA data source where more than one XA resource like Database, JMS etc.. would be involved.
Please refer to the URL: Difference between a "jta-datasource" and a " resource-local " datasource? for difference between JTA and non-JTA datasource.