[學習小結]Spring對JDBC的支持

JdbcTemplate

是什麼

特點

用法

 NamedParameterJdbcTemplate

是什麼

用法

JdbcTemplate與NamedParameterJdbcTemplate使用對比

相關配置：applicationContext.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"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	
	<context:component-scan base-package="com.atguigu.spring"></context:component-scan>
	
	<!-- 導入資源文件 -->
	<context:property-placeholder location="classpath:db.properties"/>
	
	<!-- 配置 C3P0 數據源 -->
	<bean id="dataSource"
		class="com.mchange.v2.c3p0.ComboPooledDataSource">
		<property name="user" value="${jdbc.user}"></property>
		<property name="password" value="${jdbc.password}"></property>
		<property name="jdbcUrl" value="${jdbc.jdbcUrl}"></property>
		<property name="driverClass" value="${jdbc.driverClass}"></property>

		<property name="initialPoolSize" value="${jdbc.initPoolSize}"></property>
		<property name="maxPoolSize" value="${jdbc.maxPoolSize}"></property>
	</bean>
	
	<!-- 配置 Spirng 的 JdbcTemplate -->
	<bean id="jdbcTemplate" 
		class="org.springframework.jdbc.core.JdbcTemplate">
		<property name="dataSource" ref="dataSource"></property>
	</bean>
	
	<!-- 配置 NamedParameterJdbcTemplate, 該對象可以使用具名參數, 其沒有無參數的構造器, 所以必須爲其構造器指定參數 -->
	<bean id="namedParameterJdbcTemplate"
		class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">
		<constructor-arg ref="dataSource"></constructor-arg>	
	</bean>
	</beans>

測試用例

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.sql.DataSource;

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 org.springframework.jdbc.core.namedparam.BeanPropertySqlParameterSource;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.jdbc.core.namedparam.SqlParameterSource;

public class JDBCTest {
	
	private ApplicationContext ctx = null;
	private JdbcTemplate jdbcTemplate;
	private EmployeeDao employeeDao;
	private DepartmentDao departmentDao;
	private NamedParameterJdbcTemplate namedParameterJdbcTemplate;
	
	{
		ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
		jdbcTemplate = (JdbcTemplate) ctx.getBean("jdbcTemplate");
		employeeDao = ctx.getBean(EmployeeDao.class);
		departmentDao = ctx.getBean(DepartmentDao.class);
		namedParameterJdbcTemplate = ctx.getBean(NamedParameterJdbcTemplate.class);
	}
	
	/**
	 * 使用具名參數時, 可以使用 update(String sql, SqlParameterSource paramSource) 方法進行更新操作
	 * 1. SQL 語句中的參數名和類的屬性一致!
	 * 2. 使用 SqlParameterSource 的 BeanPropertySqlParameterSource 實現類作爲參數. 
	 */
	@Test
	public void testNamedParameterJdbcTemplate2(){
		String sql = "INSERT INTO employees(last_name, email, dept_id) "
				+ "VALUES(:lastName,:email,:dpetId)";
		
		Employee employee = new Employee();
		employee.setLastName("XYZ");
		employee.setEmail("[email protected]");
		employee.setDpetId(3);
		
		SqlParameterSource paramSource = new BeanPropertySqlParameterSource(employee);
		namedParameterJdbcTemplate.update(sql, paramSource);
	}
	
	/**
	 * 可以爲參數起名字. 
	 * 1. 好處: 若有多個參數, 則不用再去對應位置, 直接對應參數名, 便於維護
	 * 2. 缺點: 較爲麻煩. 
	 */
	@Test
	public void testNamedParameterJdbcTemplate(){
		String sql = "INSERT INTO employees(last_name, email, dept_id) VALUES(:ln,:email,:deptid)";
		
		Map<String, Object> paramMap = new HashMap<>();
		paramMap.put("ln", "FF");
		paramMap.put("email", "[email protected]");
		paramMap.put("deptid", 2);
		
		namedParameterJdbcTemplate.update(sql, paramMap);
	}
	
	@Test
	public void testDepartmentDao(){
		System.out.println(departmentDao.get(1));
	}
	
	@Test
	public void testEmployeeDao(){
		System.out.println(employeeDao.get(1));
	}
	
	/**
	 * 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 employees";
		long count = jdbcTemplate.queryForObject(sql, Long.class);
		
		System.out.println(count);
	}
	
	/**
	 * 查到實體類的集合
	 * 注意調用的不是 queryForList 方法
	 */
	@Test
	public void testQueryForList(){
		String sql = "SELECT id, last_name lastName, email FROM employees WHERE id > ?";
		RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
		List<Employee> employees = jdbcTemplate.query(sql, rowMapper,5);
		
		System.out.println(employees);
	}
	
	/**
	 * 從數據庫中獲取一條記錄, 實際得到對應的一個對象
	 * 注意不是調用 queryForObject(String sql, Class<Employee> requiredType, Object... args) 方法!
	 * 而需要調用 queryForObject(String sql, RowMapper<Employee> rowMapper, Object... args)
	 * 1. 其中的 RowMapper 指定如何去映射結果集的行, 常用的實現類爲 BeanPropertyRowMapper
	 * 2. 使用 SQL 中列的別名完成列名和類的屬性名的映射. 例如 last_name lastName
	 * 3. 不支持級聯屬性. 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, last_name lastName, email, dept_id as \"department.id\" FROM employees WHERE id = ?";
		RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
		Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);
		
		System.out.println(employee);
	}
	
	/**
	 * 執行批量更新: 批量的 INSERT, UPDATE, DELETE
	 * 最後一個參數是 Object[] 的 List 類型: 因爲修改一條記錄需要一個 Object 的數組, 那麼多條不就需要多個 Object 的數組嗎
	 */
	@Test
	public void testBatchUpdate(){
		String sql = "INSERT INTO employees(last_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]", 2});
		batchArgs.add(new Object[]{"CC", "[email protected]", 3});
		batchArgs.add(new Object[]{"DD", "[email protected]", 3});
		batchArgs.add(new Object[]{"EE", "[email protected]", 2});
		
		jdbcTemplate.batchUpdate(sql, batchArgs);
	}
	
	/**
	 * 執行 INSERT, UPDATE, DELETE
	 */
	@Test
	public void testUpdate(){
		String sql = "UPDATE employees SET last_name = ? WHERE id = ?";
		jdbcTemplate.update(sql, "Jack", 5);
	}
	
	@Test
	public void testDataSource() throws SQLException {
		DataSource dataSource = ctx.getBean(DataSource.class);
		System.out.println(dataSource.getConnection());
	}

}

以上的測試例子並沒有添加事務管理，讀者注意咯！