Spring4.0学习笔记（六）

JdbcTemplate的使用

简介

JdbcTemplate是Spring框架自带的对JDBC操作的封装，目的是提供统一的模板方法使对数据库的操作更加方便、友好，效率也不错。但是功能还是不够强大（比如不支持级联属性），在实际应用中还需要和hibernate、mybaties等框架混合使用。

需要导入的jar包

c3p0-0.9.2.1.jar
commons-logging-1.1.1.jar
mchange-commons-java-0.2.3.4.jar
mysqljdbc.jar
spring-beans-4.0.2.RELEASE.jar
spring-context-4.0.2.RELEASE.jar
spring-core-4.0.2.RELEASE.jar
spring-expression-4.0.2.RELEASE.jar
spring-jdbc-4.0.2.RELEASE.jar
spring-tx-4.0.2.RELEASE.jar

源码

db.properties

jdbc.user=root
jdbc.password=1995
jdbc.driverClass=com.mysql.jdbc.Driver
jdbc.jdbcUrl=jdbc:mysql:///spring4

jdbc.initPoolSize=5
jdbc.maxPoolSize=10

<?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">

    <!-- 导入资源文件 -->
    <context:property-placeholder location="classpath:db.properties"/>

    <!-- 配置 C3P0 数据源  -->
    <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 Spring 的 JdbcTemplate -->
    <bean id="jdbcTemplate" 
        class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="dataSource"></property>
    </bean>

    <!-- 
        配置 NamedParameterJdbcTemplate , 该对象可以使用具名参数, 其没有无参数的构造器, 
        所以必须为其构造器指定参数 
    -->
    <bean id="namedParameterJdbcTemplate"
        class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">
        <constructor-arg ref="dataSource"></constructor-arg>
    </bean>
</beans>

public class Employee {

    private Integer id;
    private String lastName;
    private String email;
    private Department department;

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    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 + ", lastName=" + lastName + ", email=" + email + ", department=" + department
                + "]";
    }


}

class JDBCTest {

    private ApplicationContext ctx = null;
    private JdbcTemplate jdbcTemplate = null;
    private NamedParameterJdbcTemplate namedParam = null;

    {
        ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        jdbcTemplate = ctx.getBean(JdbcTemplate.class);
        namedParam = ctx.getBean(NamedParameterJdbcTemplate.class);
    }

    @Test
    public void testDataSource() throws SQLException {
        DataSource dataSource = (DataSource) ctx.getBean("dataSource");
        System.out.println(dataSource.getConnection());
    }

    /**
     * 执行 INSERT, UPDATE, DELETE
     */
    @Test
    public void testUpdate() {
        String sql = "UPDATE employees SET last_name = ? WHERE id = ?";
        jdbcTemplate.update(sql , "Angel2.0" , 1);
    }

    /**
     * 执行批量更新 : 批量的 INSERT, UPDATE, DELETE
     * 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 数组,
     * 那么多条就是多个 Object 数组
     */
    @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);
    }

    /**
     * 从数据库中读取一条记录, 实际得到一个对应的一个对象
     * 注意不是调用 queryForObject(String sql, Class<Employee> requiredType, Object ... args)
     * 而是调用 queryForObject(String sql, RowMapper<Employee>rowMapper, Object ... args)
     * 1. 其中的 RowMapper 指定如何去映射结果集的行, 常用的实现类为 BeanPropertyRowMapper
     * 2. 使用 SQL 中的别名完成列名和属性名的映射 例如 last_name lastName
     * 3. 不支持级联属性 JdbcTemplate 到底是一个 JDBC 的小工具, 而不是 ORM 框架
     */
    @Test
    public void testQueryForObject() {
        String sql = "SELECT id, last_name lastName, email FROM employees WHERE ID = ?";
        RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);
        Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);

        System.out.println(employee);
    }

    /**
     * 查询实体类的集合
     * 注意调用的不是 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, 3);

        System.out.println(employees);
    }

    /**
     * queryForList 可以获取某一个单个属性列的集合
     */
    @Test
    public void testQueryForList2() {
        String sql = "SELECT last_name lastName FROM employees WHERE dept_id = ?";
        List<String> list = jdbcTemplate.queryForList(sql, String.class, 3);
        System.out.println(list);
    }

    /**
     * 查询单个列的值, 或做统计查询
     * 使用 queryForObject(String sql, Class<Long> requiredType)
     */
    @Test
    public void testQueryObject2() {
        String sql = "SELECT count(id) FROM employees";
        long count = jdbcTemplate.queryForObject(sql, Long.class);

        System.out.println(count);

        sql = "SELECT last_name FROM employees WHERE id = ?";
        String lastName = jdbcTemplate.queryForObject(sql, String.class,1);

        System.out.println(lastName);
    }

    /**
     * 可以为参数起名字
     * 1. 好处 : 若有多个参数, 则不用再去对应设置, 制定对应参数名, 便于维护
     * 2. 缺点 : 较为麻烦
     */
    @Test
    public void testNamedParamterJdbcTemplat() {
        String sql = 
            "INSERT INTO employees(last_name, email, dept_id)VALUES(:ln,:email,:di)";
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("ln", "FF");
        paramMap.put("email", "[email protected]");
        paramMap.put("di", 2);
        namedParam.update(sql, paramMap);
    }

    /**
     * 使用具名参数, 可以使用 update(String sql, SqlParameterSource paramSource)
     * 1. SQL 语句中的参数名和类的属性一致！
     * 2. 使用 SqlParameterSource 的 BeanPropertySqlParameterSource 作为实现类
     */
    @Test
    public void testNamedParamterJdbcTemplat2() {
        String sql = "INSERT INTO employees(last_name, email)"
                + "VALUES(:lastName, :email)";

        Employee employee = new Employee();
        employee.setLastName("XYZ");
        employee.setEmail("[email protected]");

        SqlParameterSource paramSource = new BeanPropertySqlParameterSource(employee);
        namedParam.update(sql, paramSource);
    }

}