Spring 學習（二十一）——使用 JdbcTemplate
阿新 • • 發佈：2018-12-25
JdbcTemplate 簡介
- 為了使 JDBC 更加易於使用, Spring 在 JDBC API 上定義了一個抽象層, 以此建立一個 JDBC 存取框架.
- 作為 Spring JDBC 框架的核心, JDBC 模板的設計目的是為不同型別的 JDBC 操作提供模板方法. 每個模板方法都能控制整個過程, 並允許覆蓋過程中的特定任務. 通過這種方式, 可以在儘可能保留靈活性的情況下, 將資料庫存取的工作量降到最低.
使用 JdbcTemplate 更新資料庫
- 用 sql 語句和引數更新資料庫
public void testUpdate() { String sql = "update employee set name = ? where id = ?"; int row = jdbcTemplate.update(sql, "Rose", 4); System.out.println(row); }
- 批量更新資料庫
public void testBatchUpdate() { String sql = "insert into employee (name, email, dept_id) values (?, ?, ?)"; List<Object[]> batchArgs = new ArrayList<>(); batchArgs.add(new Object[]{"AA", "[email protected]", 1}); batchArgs.add(new Object[]{"BB", "[email protected]", 3}); batchArgs.add(new Object[]{"CC", "[email protected]", 4}); batchArgs.add(new Object[]{"DD", "[email protected]", 3}); batchArgs.add(new Object[]{"EE", "[email protected]", 2}); int[] result = jdbcTemplate.batchUpdate(sql, batchArgs); System.out.println(Arrays.toString(result)); }
使用 JdbcTemplate 查詢資料庫
- 查詢單行
public void testQueryForObject() {
String sql = "SELECT id, name, email, dept_id FROM employee WHERE id = ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);
System.out.println(employee);
}- 便利的 BeanPropertyRowMapper 實現
- 查詢多行
public void testQueryForList() {
String sql = "SELECT id, name, email FROM employee WHERE id > ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
List<Employee> employees = jdbcTemplate.query(sql, rowMapper, 5);
System.out.println(employees);
}- 單值查詢:
public void testQueryForObject() {
String sql = "SELECT count(id) FROM employee WHERE id > ?";
long count = jdbcTemplate.queryForObject(sql, Long.class, 5);
System.out.println(count);
}簡化 JDBC 模板查詢
- 每次使用都建立一個 JdbcTemplate 的新例項, 這種做法效率很低下.
- JdbcTemplate 類被設計成為執行緒安全的, 所以可以再 IOC 容器中宣告它的單個例項, 並將這個例項注入到所有的 DAO 例項中.
- JdbcTemplate 也利用了 Java 1.5 的特定(自動裝箱, 泛型, 可變長度等)來簡化開發
- Spring JDBC 框架還提供了一個 JdbcDaoSupport 類來簡化 DAO 實現. 該類聲明瞭 jdbcTemplate 屬性, 它可以從 IOC 容器中注入, 或者自動從資料來源中建立.
注入 JDBC 模板示例程式碼
擴充套件 JdbcDaoSupport 示例程式碼
程式碼示例：
1、資料庫表的建立如下：
employee表
department表
2、目錄結構
Spring
|——src
|——|——com.hzyc.spring.jdbc
|——|——|——department.java
|——|——|——departmentDao.java
|——|——|——employee.java
|——|——|——employeeDao.java
|——|——|——JdbcTest.java
|——|——application-context.xml
|——|——db.properties
2、db.properties
jdbc.driverClass=com.mysql.jdbc.Driver
jdbc.jdbcUrl=jdbc:mysql:///spring
jdbc.user=root
jdbc.password=root
jdbc.initPoolSize=5
jdbc.maxPoolSize=10
3、application-context.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"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd">
<context:component-scan base-package="com.hzyc.spring"/>
<!--匯入資原始檔-->
<context:property-placeholder location="classpath:db.properties"/>
<!--配置 c3p0 資料來源-->
<bean id="dataSource"
class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="${jdbc.driverClass}"/>
<property name="jdbcUrl" value="${jdbc.jdbcUrl}"/>
<property name="user" value="${jdbc.user}"/>
<property name="password" value="${jdbc.password}"/>
<property name="initialPoolSize" value="${jdbc.initPoolSize}"/>
<property name="maxPoolSize" value="${jdbc.maxPoolSize}"/>
</bean>
<!--配置 Spring 的 Jdbc Template-->
<bean id="jdbcTemplate"
class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"/>
</bean>
</beans>department.java
package com.hzyc.spring.jdbc;
/**
* @author xuehj2016
* @Title: Department
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 14:43
*/
public class Department {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Department{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}departmentDao.java
package com.hzyc.spring.jdbc;
import javax.sql.DataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.core.support.JdbcDaoSupport;
import org.springframework.stereotype.Repository;
/**
* @author xuehj2016
* @Title: DepartmentDao
* @ProjectName Spring
* @Description: 不推薦使用 JdbcDaoSupport, 而推薦直接使用 JdbcTemplate 作為 Dao 類的成員變數
* @date 2018/12/21 18:34
*/
@Repository
public class DepartmentDao extends JdbcDaoSupport {
@Autowired
public void setDataSource2(DataSource dataSource) {
setDataSource(dataSource);
}
public Department get(int id) {
String sql = "SELECT id, name FROM department WHERE id = ?";
RowMapper<Department> rowMapper = new BeanPropertyRowMapper<>(Department.class);
return getJdbcTemplate().queryForObject(sql, rowMapper, id);
}
}employee.java
package com.hzyc.spring.jdbc;
/**
* @author xuehj2016
* @Title: Employee
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 14:41
*/
public class Employee {
private int id;
private String name;
private String email;
private Department department;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Department getDepartment() {
return department;
}
public void setDepartment(Department department) {
this.department = department;
}
@Override
public String toString() {
return "Employee{" +
"id=" + id +
", name='" + name + '\'' +
", email='" + email + '\'' +
", department=" + department +
'}';
}
}employeeDao.java
package com.hzyc.spring.jdbc;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;
/**
* @author xuehj2016
* @Title: EmployeeDao
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 18:35
*/
@Repository
public class EmployeeDao {
@Autowired
private JdbcTemplate jdbcTemplate;
public Employee get(int id) {
String sql = "SELECT id, name, email FROM employee WHERE id = ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, id);
return employee;
}
}JdbcTest.java
package com.hzyc.spring.jdbc;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import javax.sql.DataSource;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @author xuehj2016
* @Title: JdbcTest
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/21 14:02
*/
public class JdbcTest {
private ApplicationContext applicationContext;
private JdbcTemplate jdbcTemplate;
private EmployeeDao employeeDao;
private DepartmentDao departmentDao;
{
applicationContext = new ClassPathXmlApplicationContext("application-context.xml");
jdbcTemplate = (JdbcTemplate) applicationContext.getBean("jdbcTemplate");
employeeDao = (EmployeeDao) applicationContext.getBean("employeeDao");
departmentDao = (DepartmentDao) applicationContext.getBean("departmentDao");
}
@Test
public void testDataSource() throws SQLException {
DataSource dataSource = (DataSource) applicationContext.getBean("dataSource");
System.out.println(dataSource.getConnection());
}
/**
* 執行 insert ，update ， delete
*/
@Test
public void testUpdate() {
String sql = "update employee set name = ? where id = ?";
int row = jdbcTemplate.update(sql, "Rose", 4);
System.out.println(row);
}
/**
* 執行批量更新 : 批量的 insert ，update ，delete
* 最後一個引數是 Object[] 的 List 型別；因為修改一條記錄需要一個 Object 的陣列，多條就需要多個 Object 的陣列
*/
@Test
public void testBatchUpdate() {
String sql = "insert into employee (name, email, dept_id) values (?, ?, ?)";
List<Object[]> batchArgs = new ArrayList<>();
batchArgs.add(new Object[]{"AA", "[email protected]", 1});
batchArgs.add(new Object[]{"BB", "[email protected]", 3});
batchArgs.add(new Object[]{"CC", "[email protected]", 4});
batchArgs.add(new Object[]{"DD", "[email protected]", 3});
batchArgs.add(new Object[]{"EE", "[email protected]", 2});
int[] result = jdbcTemplate.batchUpdate(sql, batchArgs);
System.out.println(Arrays.toString(result));
}
/**
* 從資料庫中獲取一條記錄, 實際得到對應的一個物件
* 注意不是呼叫 queryForObject(String sql, Class<Employee> requiredType, Object... args) 方法!
* 而需要呼叫 queryForObject(String sql, RowMapper<Employee> rowMapper, Object... args)
* 1. 其中的 RowMapper 指定如何去對映結果集的行, 常用的實現類為 BeanPropertyRowMapper
* 2. 使用 SQL 中列的別名完成列名和類的屬性名的對映. 例如 dept_id as department.id
* 3. 不支援級聯屬性. JdbcTemplate 到底是一個 JDBC 的小工具, 而不是 ORM 框架
*/
@Test
public void testQueryForObject() {
String sql = "SELECT id, name, email, dept_id FROM employee WHERE id = ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);
System.out.println(employee);
}
/**
* 查到實體類的集合
* 注意呼叫的不是 queryForList 方法，而是 query 方法
*/
@Test
public void testQueryForList() {
String sql = "SELECT id, name, email FROM employee WHERE id > ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
List<Employee> employees = jdbcTemplate.query(sql, rowMapper, 5);
System.out.println(employees);
}
/**
* 獲取單個列的值, 或做統計查詢
* 使用 queryForObject(String sql, Class<Long> requiredType)
*/
@Test
public void testQueryForObject2() {
String sql = "SELECT count(id) FROM employee WHERE id > ?";
long count = jdbcTemplate.queryForObject(sql, Long.class, 5);
System.out.println(count);
}
@Test
public void testEmployeeDao() {
System.out.println(employeeDao.get(1));
}
@Test
public void testDepartmentDao() {
System.out.println(departmentDao.get(1));
}
}