JDBC 框架概述

在使用普通的 JDBC 數據庫時，就會很麻煩的寫不必要的代碼來處理異常，打開和關閉數據庫連接等。但 Spring JDBC 框架負責所有的低層細節，從開始打開連接，準備和執行 SQL 語句，處理異常，處理事務，到最後關閉連接。

所以當從數據庫中獲取數據時，你所做的是定義連接參數，指定要執行的 SQL 語句，每次叠代完成所需的工作。

Spring JDBC 提供幾種方法和數據庫中相應的不同的類與接口。我將給出使用 JdbcTemplate 類框架的經典和最受歡迎的方法。這是管理所有數據庫通信和異常處理的中央框架類。

JdbcTemplate 類

JdbcTemplate 類執行 SQL 查詢、更新語句和存儲過程調用，執行叠代結果集和提取返回參數值。它也捕獲 JDBC 異常並轉換它們到 org.springframework.dao 包中定義的通用類、更多的信息、異常層次結構。

JdbcTemplate 類的實例是線程安全配置的。所以你可以配置 JdbcTemplate 的單個實例，然後將這個共享的引用安全地註入到多個 DAOs 中。

使用 JdbcTemplate 類時常見的做法是在你的 Spring 配置文件中配置數據源，然後共享數據源 bean 依賴註入到 DAO 類中，並在數據源的設值函數中創建了 JdbcTemplate。

演示示例如下:

(1)建立mysql數據庫，並導入該腳本，庫名可任意命名，這裏命名為test,sql腳本為:

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

(2)創建實體

package com.tutorialspoint;
public class Student {
   private Integer age;
   private String name;
   private Integer id;
   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;
   }
}

(3)創建DAO

package com.tutorialspoint;
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 table.
    */
   public void create(String name, Integer age);
   /** 
    * This is the method to be used to list down
    * a record from the Student table corresponding
    * to a passed student id.
    */
   public Student getStudent(Integer id);
   /** 
    * This is the method to be used to list down
    * all the records from the Student table.
    */
   public List<Student> listStudents();
   /** 
    * This is the method to be used to delete
    * a record from the Student table corresponding
    * to a passed student id.
    */
   public void delete(Integer id);
   /** 
    * This is the method to be used to update
    * a record into the Student table.
    */
   public void update(Integer id, Integer age);
}

(4)創建StudentMapper

package com.tutorialspoint;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;
public class StudentMapper implements RowMapper<Student> {
   public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
      Student student = new Student();
      student.setId(rs.getInt("id"));
      student.setName(rs.getString("name"));
      student.setAge(rs.getInt("age"));
      return student;
   }
}

(5)創建StudentJDBCTemplate

package com.tutorialspoint;
import java.util.List;
import javax.sql.DataSource;
import org.springframework.jdbc.core.JdbcTemplate;
public class StudentJDBCTemplate implements StudentDAO {
   private DataSource dataSource;
   private JdbcTemplate jdbcTemplateObject; 
   public void setDataSource(DataSource dataSource) {
      this.dataSource = dataSource;
      this.jdbcTemplateObject = new JdbcTemplate(dataSource);
   }
   public void create(String name, Integer age) {
      String SQL = "insert into Student (name, age) values (?, ?)";     
      jdbcTemplateObject.update( SQL, name, age);
      System.out.println("Created Record Name = " + name + " Age = " + age);
      return;
   }
   public Student getStudent(Integer id) {
      String SQL = "select * from Student where id = ?";
      Student student = jdbcTemplateObject.queryForObject(SQL, 
                        new Object[]{id}, new StudentMapper());
      return student;
   }
   public List<Student> listStudents() {
      String SQL = "select * from Student";
      List <Student> students = jdbcTemplateObject.query(SQL, 
                                new StudentMapper());
      return students;
   }
   public void delete(Integer id){
      String SQL = "delete from Student where id = ?";
      jdbcTemplateObject.update(SQL, id);
      System.out.println("Deleted Record with ID = " + id );
      return;
   }
   public void update(Integer id, Integer age){
      String SQL = "update Student set age = ? where id = ?";
      jdbcTemplateObject.update(SQL, age, id);
      System.out.println("Updated Record with ID = " + id );
      return;
   }
}

(6)編寫對應的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://localhost:3306/test"/>
      <property name="username" value="root"/>
      <property name="password" value="1234"/>
   </bean>

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

</beans>

(7)編寫MainApp.java並運行

package com.tutorialspoint;
import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
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);
          studentJDBCTemplate.create("Nuha", 2);
          studentJDBCTemplate.create("Ayan", 15);
          System.out.println("------Listing Multiple Records--------" );
          List<Student> students = studentJDBCTemplate.listStudents();
          for (Student record : students) {
             System.out.print("ID : " + record.getId() );
             System.out.print(", Name : " + record.getName() );
             System.out.println(", Age : " + record.getAge());
          }
          System.out.println("----Updating Record with ID = 2 -----" );
          studentJDBCTemplate.update(2, 20);
          System.out.println("----Listing Record with ID = 2 -----" );
          Student student = studentJDBCTemplate.getStudent(2);
          System.out.print("ID : " + student.getId() );
          System.out.print(", Name : " + student.getName() );
          System.out.println(", Age : " + student.getAge());      
       }
}

運行結果如下:

數據表數據由無變為有:

Spring(十二)之JDBC框架