Spring 編程式事務管理
編程式事務管理辦法允許您管理與編程的源代碼的幫助下事務。這就給了極大的靈活性,但它難以維護。
在我們開始之前,它至少有兩個數據庫表上,我們可以在事務的幫助下執行各種CRUD操作。讓我們以Student表,它可以在MySQL數據庫中測試用下麵的DDL創建:
CREATE TABLE Student( ID INT NOT NULL AUTO_INCREMENT, NAME VARCHAR(20) NOT NULL, AGE INT NOT NULL, PRIMARY KEY (ID) );
第二個表是Marks,我們將保持標記為基於多年的學生。這裡SID是表表的外鍵。
CREATE TABLE Marks( SID INT NOT NULL, MARKS INT NOT NULL, YEAR INT NOT NULL );
讓我們使用PlatformTransactionManager直接實現編程的方法來實現事務。要開始一個新的事務,需要有TransactionDefinition 適當的事務屬性的一個實例。在這個例子中,我們將簡單地創建DefaultTransactionDefinition的實例使用默認的事務屬性。
一旦TransactionDefinition被創建,你可以通過調用getTransaction()方法,它返回的TransactionStatus對象的一個實例開始事務。TransactionStatus對象有助於跟蹤事務的當前狀態,最後,如果一切順利,可以使用提交(的PlatformTransactionManager的)方法來提交事務,否則可以使用rollback() 回滾完成操作。
現在我們編寫Spring JDBC應用程序,將實現Student和Marks表簡單的操作。使用Eclipse IDE,然後按照下麵的步驟來創建一個Spring應用程序:
步驟 | 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. |
以下是數據訪問對象接口文件StudentDAO.java的內容:
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文件的內容:
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文件的內容:
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; } }
下麵是實現類文件StudentJDBCTemplate.java的定義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; } }
現在讓我們移動主應用程序文件MainApp.java,這是如下:
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>
創建源代碼和bean配置文件完成後,讓我們運行應用程序。如果一切順利,這將打印以下信息:
------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