Spring 编程式事务管理

编程式事务管理办法允许您管理与编程的源代码的帮助下事务。这就给了极大的灵活性，但它难以维护。

在我们开始之前，它至少有两个数据库表上，我们可以在事务的帮助下执行各种CRUD操作。让我们以Student表，它可以在MySQL数据库中测试用下面的DDL创建：

CREATE TABLE Student(
   ID   INT NOT NULL AUTO_INCREMENT,
   NAME VARCHAR(20) NOT NULL,
   AGE  INT NOT NULL,
   PRIMARY KEY (ID)
);

第二个表是Marks，我们将保持标记为基于多年的学生。这里SID是表表的外键。

CREATE TABLE Marks(
   SID INT NOT NULL,
   MARKS  INT NOT NULL,
   YEAR   INT NOT NULL
);

让我们使用PlatformTransactionManager直接实现编程的方法来实现事务。要开始一个新的事务，需要有TransactionDefinition 适当的事务属性的一个实例。在这个例子中，我们将简单地创建DefaultTransactionDefinition的实例使用默认的事务属性。

一旦TransactionDefinition被创建，你可以通过调用getTransaction()方法，它返回的TransactionStatus对象的一个实例开始事务。TransactionStatus对象有助于跟踪事务的当前状态，最后，如果一切顺利，可以使用提交（的PlatformTransactionManager的）方法来提交事务，否则可以使用rollback() 回滚完成操作。

现在我们编写Spring JDBC应用程序，将实现Student和Marks表简单的操作。使用Eclipse IDE，然后按照下面的步骤来创建一个Spring应用程序：

步骤	描述
1	Create a project with a name SpringExample and create a package com.yiibai under the src folder in the created project.
2	Add required Spring libraries using Add External JARs option as explained in the Spring Hello World Example chapter.
3	Add Spring JDBC specific latest libraries mysql-connector-java.jar,org.springframework.jdbc.jar and org.springframework.transaction.jar in the project. You can download required libraries if you do not have them already.
4	Create DAO interface StudentDAO and list down all the required methods. Though it is not required and you can directly write StudentJDBCTemplate class, but as a good practice, let's do it.
5	Create other required Java classes StudentMarks, StudentMarksMapper,StudentJDBCTemplate and MainApp under the com.yiibai package. You can create rest of the POJO classes if required.
6	Make sure you already created Student and Marks tables in TEST database. Also make sure your MySQL server is working fine and you have read/write access on the database using the give username and password.
7	Create Beans configuration file Beans.xml under the src folder.
8	The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below.

以下是数据访问对象接口文件StudentDAO.java的内容：

package com.yiibai;

import java.util.List;
import javax.sql.DataSource;

public interface StudentDAO {
   /** 
    * This is the method to be used to initialize
    * database resources ie. connection.
    */
   public void setDataSource(DataSource ds);
   /** 
    * This is the method to be used to create
    * a record in the Student and Marks tables.
    */
   public void create(String name, Integer age, Integer marks, Integer year);
   /** 
    * This is the method to be used to list down
    * all the records from the Student and Marks tables.
    */
   public List<StudentMarks> listStudents();
}

以下是StudentMarks.java文件的内容：

package com.yiibai;

public class StudentMarks {
   private Integer age;
   private String name;
   private Integer id;
   private Integer marks;
   private Integer year;
   private Integer sid;

   public void setAge(Integer age) {
      this.age = age;
   }
   public Integer getAge() {
      return age;
   }

   public void setName(String name) {
      this.name = name;
   }
   public String getName() {
      return name;
   }

   public void setId(Integer id) {
      this.id = id;
   }
   public Integer getId() {
      return id;
   }
   public void setMarks(Integer marks) {
      this.marks = marks;
   }
   public Integer getMarks() {
      return marks;
   }

   public void setYear(Integer year) {
      this.year = year;
   }
   public Integer getYear() {
      return year;
   }

   public void setSid(Integer sid) {
      this.sid = sid;
   }
   public Integer getSid() {
      return sid;
   }
}

以下是StudentMarksMapper.java文件的内容：

package com.yiibai;

import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;

public class StudentMarksMapper implements RowMapper<StudentMarks> {
   public StudentMarks mapRow(ResultSet rs, int rowNum) throws SQLException {

      StudentMarks studentMarks = new StudentMarks();

      studentMarks.setId(rs.getInt("id"));
      studentMarks.setName(rs.getString("name"));
      studentMarks.setAge(rs.getInt("age"));
      studentMarks.setSid(rs.getInt("sid"));
      studentMarks.setMarks(rs.getInt("marks"));
      studentMarks.setYear(rs.getInt("year"));

      return studentMarks;
   }
}

下面是实现类文件StudentJDBCTemplate.java的定义DAO接口StudentDAO：

package com.yiibai;

import java.util.List;
import javax.sql.DataSource;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.DefaultTransactionDefinition;

public class StudentJDBCTemplate implements StudentDAO {
   private DataSource dataSource;
   private JdbcTemplate jdbcTemplateObject;
   private PlatformTransactionManager transactionManager;

   public void setDataSource(DataSource dataSource) {
      this.dataSource = dataSource;
      this.jdbcTemplateObject = new JdbcTemplate(dataSource);
   }

   public void setTransactionManager(
      PlatformTransactionManager transactionManager) {
      this.transactionManager = transactionManager;
   }

   public void create(String name, Integer age, Integer marks, Integer year){

      TransactionDefinition def = new DefaultTransactionDefinition();
      TransactionStatus status = transactionManager.getTransaction(def);

      try {
         String SQL1 = "insert into Student (name, age) values (?, ?)";
         jdbcTemplateObject.update( SQL1, name, age);

         // Get the latest student id to be used in Marks table
         String SQL2 = "select max(id) from Student";
         int sid = jdbcTemplateObject.queryForInt( SQL2 );

         String SQL3 = "insert into Marks(sid, marks, year) " + 
                       "values (?, ?, ?)";
         jdbcTemplateObject.update( SQL3, sid, marks, year);

         System.out.println("Created Name = " + name + ", Age = " + age);
         transactionManager.commit(status);
      } catch (DataAccessException e) {
         System.out.println("Error in creating record, rolling back");
         transactionManager.rollback(status);
         throw e;
      }
      return;
   }

   public List<StudentMarks> listStudents() {
      String SQL = "select * from Student, Marks where Student.id=Marks.sid";

      List <StudentMarks> studentMarks = jdbcTemplateObject.query(SQL, 
                                         new StudentMarksMapper());
      return studentMarks;
   }
}

现在让我们移动主应用程序文件MainApp.java，这是如下：

package com.yiibai;
import java.util.List;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.yiibai.StudentJDBCTemplate;

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = 
             new ClassPathXmlApplicationContext("Beans.xml");

      StudentJDBCTemplate studentJDBCTemplate = 
      (StudentJDBCTemplate)context.getBean("studentJDBCTemplate");
      
      System.out.println("------Records creation--------" );
      studentJDBCTemplate.create("Zara", 11, 99, 2010);
      studentJDBCTemplate.create("Nuha", 20, 97, 2010);
      studentJDBCTemplate.create("Ayan", 25, 100, 2011);

      System.out.println("------Listing all the records--------" );
      List<StudentMarks> studentMarks = studentJDBCTemplate.listStudents();
      for (StudentMarks record : studentMarks) {
         System.out.print("ID : " + record.getId() );
         System.out.print(", Name : " + record.getName() );
         System.out.print(", Marks : " + record.getMarks());
         System.out.print(", Year : " + record.getYear());
         System.out.println(", Age : " + record.getAge());
      }
   }
}

以下是配置文件beans.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd ">

   <!-- Initialization for data source -->
   <bean id="dataSource" 
      class="org.springframework.jdbc.datasource.DriverManagerDataSource">
      <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
      <property name="url" value="jdbc:mysql://localhost:3306/TEST"/>
      <property name="username" value="root"/>
      <property name="password" value="password"/>
   </bean>

   <!-- Initialization for TransactionManager -->
   <bean id="transactionManager" 
      class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
      <property name="dataSource"  ref="dataSource" />    
   </bean>

   <!-- Definition for studentJDBCTemplate bean -->
   <bean id="studentJDBCTemplate"
      class="com.yiibai.StudentJDBCTemplate">
      <property name="dataSource"  ref="dataSource" />
      <property name="transactionManager"  ref="transactionManager" />    
   </bean>
      
</beans>

创建源代码和bean配置文件完成后，让我们运行应用程序。如果一切顺利，这将打印以下信息：

------Records creation--------
Created Name = Zara, Age = 11
Created Name = Nuha, Age = 20
Created Name = Ayan, Age = 25
------Listing all the records--------
ID : 1, Name : Zara, Marks : 99, Year : 2010, Age : 11
ID : 2, Name : Nuha, Marks : 97, Year : 2010, Age : 20
ID : 3, Name : Ayan, Marks : 100, Year : 2011, Age : 25

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