Spring 程序化事务管理

程序化事务管理

程序化事务管理方法使您可以借助源代码中的编程来管理事务。这为您提供了极大的灵活性，但是很难维护。在开始之前，重要的是至少要有两个数据库表，我们可以在这些数据库表上借助事务来执行各种CRUD操作。让我们考虑一个学生表，该表可以在MySQL test数据库中使用以下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，我们将维护基于多年的学生痕迹。这里SID是学生表的ID。

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

让我们直接使用PlatformTransactionManager来实现编程方法来实现事务。要开始新事务，您需要具有带有适当事务属性的TransactionDefinition实例。对于此示例，我们将简单地创建DefaultTransactionDefinition的实例以使用默认事务属性。创建TransactionDefinition之后，您可以通过调用getTransaction()方法开始事务，该方法返回TransactionStatus的实例。TransactionStatus对象有助于跟踪事务的当前状态，最后，如果一切顺利，你可以使用PlatformTransactionManager的commit()方法提交事务，否则，你可以使用rollback()回滚完成操作。现在，让我们编写我们的Spring JDBC应用程序，该应用程序将对Student和Marks表执行简单的操作。

让我们拥有一个运行良好的Eclipse IDE，并采取以下步骤来创建一个Spring应用程序：

创建一个名称为SpringExample的项目，并在创建的项目的src文件夹下创建一个包com.jc2182。
使用“添加外部JAR”选项添加所需的Spring库，如“Spring Hello World示例”一章中所述。
在项目中添加特定于Spring JDBC的最新库mysql-connector-java.jar，org.springframework.jdbc.jar和 org.springframework.transaction.jar如果尚未下载所需的库，则可以下载它们。
创建DAO界面StudentDAO并列出所有必需的方法。尽管这不是必需的，并且您可以直接编写StudentJDBCTemplate类，但是作为一个好习惯，让我们开始吧。
在com.jc2182包下创建其他所需的Java类StudentMarks，StudentMarksMapper，StudentJDBCTemplate和MainApp。
确保您已经在test数据库中创建了Student和Marks表。另外，请确保您的MySQL服务器运行正常，并使用用户名和密码对数据库具有读/写访问权限。
在src文件夹下创建Beans配置文件Beans.xml。
最后一步是创建所有Java文件和Bean配置文件的内容，然后按以下说明运行应用程序。

以下是数据访问对象接口文件StudentDAO.java的内容


package com.jc2182;

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.jc2182;

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.jc2182;

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;
   }
}

以下是已定义的DAO接口StudentDAO的实现类文件StudentJDBCTemplate.java


package com.jc2182;

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.queryForObject( SQL2 ,Integer.class );

         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，如下所示-


package com.jc2182;

import java.util.List;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jc2182.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


<?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://192.168.61.125:3306/test"/>
      <property name = "username" value = "root"/>
      <property name = "password" value = "123456"/>
   </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.jc2182.StudentJDBCTemplate">
      <property name = "dataSource" ref = "dataSource" />
      <property name = "transactionManager" ref = "transactionManager" />    
   </bean>
      
</beans>

完成创建源和Bean配置文件后，让我们运行该应用程序。如果您的应用程序一切正常，它将显示以下消息：


------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