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
