Spring--JdbcTemplate

JdbcTemplate简介

1. 为了使JDBC更加易于使用，Spring在JDBC API上定义了一个抽象层，以此建立一个JDBC存取框架
2. 作为Spring JDBC框架的核心，JDBC模板的设计目的是为不同类型的JDBC操作提供模板方法，每个模板方法都能控制整个过程，并允许覆盖过程中的特定任务。通过这种方式，可以在尽可能保留灵活性的情况下，将数据库存取的工作量降到最低。

代码示例：

首先是数据库的配置。数据库中包含employee和department两张表。

1 jdbc.user=scott
2 jdbc.password=tiger
3 jdbc.driverClass=oracle.jdbc.driver.OracleDriver
4 jdbc.jdbcUrl=jdbc:oracle:thin:@localhost:1521:orcl
5 
6 jdbc.initialPoolSize=5
7 jdbc.maxPoolSize=10

然后是spring的配置文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xmlns:context="http://www.springframework.org/schema/context"
 5     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
 6         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd">
 7 
 8     <context:component-scan base-package="com.yl.spring.jdbc"></context:component-scan>
 9 
10     <!-- 导入属性文件 -->
11     <context:property-placeholder location="classpath:db.properties"/>
12     <!-- 配置c3p0数据源 -->
13     <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
14         <property name="user" value="${jdbc.user}"></property>
15         <property name="password" value="${jdbc.password}"></property>
16         <property name="driverClass" value="${jdbc.driverClass}"></property>
17         <property name="jdbcUrl" value="${jdbc.jdbcUrl}"></property>
18         
19         <property name="initialPoolSize" value="${jdbc.initialPoolSize}"></property>
20         <property name="maxPoolSize" value="${jdbc.maxPoolSize}"></property>
21     </bean>
22 
23     <!-- 配置Spring的JdbcTemplate -->
24     <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
25         <property name="dataSource" ref="dataSource"></property>
26     </bean>
27 </beans>

然后是两个实体类:Employee和Department

 1 package com.yl.spring.jdbc;
 2 
 3 public class Employee {
 4     private Integer id;
 5     private String lastName;
 6     private String email;
 7     
 8     private Department department;
 9 
10     public Integer getId() {
11         return id;
12     }
13 
14     public void setId(Integer id) {
15         this.id = id;
16     }
17 
18     public String getLastName() {
19         return lastName;
20     }
21 
22     public void setLastName(String lastName) {
23         this.lastName = lastName;
24     }
25 
26     public String getEmail() {
27         return email;
28     }
29 
30     public void setEmail(String email) {
31         this.email = email;
32     }
33 
34     public Department getDepartment() {
35         return department;
36     }
37 
38     public void setDepartment(Department department) {
39         this.department = department;
40     }
41 
42     @Override
43     public String toString() {
44         return "Employee [id=" + id + ", lastName=" + lastName + ", email="
45                 + email + ", department=" + department + "]";
46     }
47     
48     
49 }

 1 package com.yl.spring.jdbc;
 2 
 3 public class Department {
 4     private Integer id;
 5     private String name;
 6     public Integer getId() {
 7         return id;
 8     }
 9     public void setId(Integer id) {
10         this.id = id;
11     }
12     public String getName() {
13         return name;
14     }
15     public void setName(String name) {
16         this.name = name;
17     }
18     @Override
19     public String toString() {
20         return "Department [id=" + id + ", name=" + name + "]";
21     }
22     
23     
24 }

然后是测试类

  1 package com.yl.spring.jdbc;
  2 
  3 
  4 import java.sql.SQLException;
  5 import java.util.ArrayList;
  6 import java.util.List;
  7 
  8 import javax.sql.DataSource;
  9 
 10 import org.junit.Test;
 11 import org.springframework.context.ApplicationContext;
 12 import org.springframework.context.support.ClassPathXmlApplicationContext;
 13 import org.springframework.jdbc.core.BeanPropertyRowMapper;
 14 import org.springframework.jdbc.core.JdbcTemplate;
 15 import org.springframework.jdbc.core.RowMapper;
 16 
 17 public class JDBCTest {
 18     
 19     private ApplicationContext ctx = null;
 20     private JdbcTemplate jdbcTemplate;
 21     private EmployeeDao employeeDao;
 22     
 23     {
 24         ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
 25         jdbcTemplate = (JdbcTemplate)ctx.getBean("jdbcTemplate");
 26         employeeDao = ctx.getBean(EmployeeDao.class);
 27     }
 28     
 29     @Test
 30     public void testEmployeeDao() {
 31         System.out.println(employeeDao.get(1));
 32     }
 33     
 34     /**
 35      * 获取单个列的值，或做统计查询
 36      */
 37     @Test
 38     public void testQueryForObject2() {
 39         String sql = "SELECT count(id) FROM employee";
 40         long count = jdbcTemplate.queryForObject(sql, Long.class);
 41         System.out.println(count);
 42     }
 43     
 44     /**
 45      * 查到实体类的集合
 46      */
 47     @Test
 48     public void testQueryForList() {
 49         String sql = "SELECT id, last_name, email FROM employee WHERE id > ?";
 50         RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);
 51         List<Employee> employees = jdbcTemplate.query(sql, rowMapper, 5);
 52         System.out.println(employees);
 53     }
 54     
 55     /**
 56      * 从数据库中获取一条记录，实际得到对应的一个对象
 57      * 1.RowMapper指定如何映射结果集的行，常用的实现类为BeanPropertyRowMapper
 58      * 2.使用SQL中列的别名完成列名和类的属性名的映射。例如last_name和lastName
 59      * 3.不支持级联属性。JdbcTemplate到底是一个JDBC工具，不是ORM框架。
 60      */
 61     @Test
 62     public void TestForQueryObject() {
 63         String sql = "SELECT id, last_name, email FROM employee WHERE id = ?";
 64         RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);
 65         
 66         Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);
 67         System.out.println(employee);
 68     }
 69     
 70     /**
 71      * 批量执行更新：批量的INSERT, UPDATE, DELETE
 72      * 最后一个参数是Object[]的list类型：因为修改一条记录需要一个Object的数组，那么多条就是需要多个Object的数组
 73      */
 74     @Test
 75     public void testBatchUpdate() {
 76         String sql = "INSERT INTO employee(id, last_name, email, dept_id) VALUES(?, ?, ?, ?)";
 77         List<Object[]> batchArgs = new ArrayList<Object[]>();
 78         batchArgs.add(new Object[]{6, "AA", "[email protected]", 1});
 79         batchArgs.add(new Object[]{7, "BB", "[email protected]", 2});
 80         batchArgs.add(new Object[]{8, "CC", "[email protected]", 3});
 81         batchArgs.add(new Object[]{9, "DD", "[email protected]", 3});
 82         batchArgs.add(new Object[]{10, "EE", "[email protected]", 2});
 83         jdbcTemplate.batchUpdate(sql, batchArgs);
 84     }
 85     
 86     /**
 87      * 执行INSERT, UPDATE, DELETE
 88      */
 89     @Test
 90     public void testUpdate() {
 91         String sql = "UPDATE employee SET last_name=? WHERE id=?";
 92         jdbcTemplate.update(sql, "Jack", 5);
 93     }
 94     
 95     @Test
 96     public void test() throws SQLException {
 97         DataSource dataSource = (DataSource)ctx.getBean("dataSource");
 98         System.out.println(dataSource.getConnection());
 99     }
100 
101 }

如果在项目中使用JdbcTemplate，那么可以参考下面的写法来写对应的dao：

 1 package com.yl.spring.jdbc;
 2 
 3 import org.springframework.beans.factory.annotation.Autowired;
 4 import org.springframework.jdbc.core.BeanPropertyRowMapper;
 5 import org.springframework.jdbc.core.JdbcTemplate;
 6 import org.springframework.jdbc.core.RowMapper;
 7 import org.springframework.stereotype.Repository;
 8 
 9 @Repository
10 public class EmployeeDao {
11     
12     @Autowired
13     private JdbcTemplate jdbcTemplate;
14     
15     public Employee get(Integer id) {
16         String sql = "SELECT id, last_name, email FROM employee WHERE id = ?";
17         RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);
18         
19         Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, id);
20         
21         return employee;
22     }
23 }