spring 系列 8-jdbcTemplate

JdbcTemplate是spring对JDBC的封装，目的是使JDBC更易于使用，JdbcTemplate是Spring的一部分，JdbcTemplate处理了资源的建立和释放，帮我们避免一些常见的错误，比如忘记关闭连接。它运行核心的JDBC工作流，如Statement的建立和执行，而我们只需要提供SQL语句和提取结果。

提供的操作模板类：

• 操作关系型数据库
  • JdbcTemplate
  • HibernateTemplate
• 操作nosql数据库
  • RedisTemplate
• 操作消息队列
  • JmsTemplate

JdbcTemplate的基本使用

首先添加坐标：

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.2.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

实体类：

public class Account implements Serializable {
    private Integer id;
    private String name;
    private Float money;
    //省略get、set、toString方法
}

测试：

        DriverManagerDataSource ds = new DriverManagerDataSource();
        ds.setDriverClassName("com.mysql.jdbc.Driver");
        ds.setUrl("jdbc:mysql://localhost:3306/db4");
        ds.setUsername("root");
        ds.setPassword("123456");

        JdbcTemplate jt = new JdbcTemplate();
        jt.setDataSource(ds);
        jt.execute("insert into account(name,money)values('张三',1000)");//执行
        //保存
        //jt.update("insert into account(name,money)values(?,?)", "李四", 100);
        //更新
        //jt.update("update account set money=money-? where id=?",3,100);
        //删除
        //jt.update("delete from account where id=?",3);
        //查询所有
        //List<Account> accounts = jt.query("select * from account where money>?", new AccountRowMapper(), 500f);
        //查询所有简化版,不用写RowMapper的实现类
        //List<Account> accounts = jt.query("select * from account where money>?", new BeanPropertyRowMapper<Account>(Account.class),500f);
        //for (Account account : accounts) {
        //    System.out.println(account);
        //}
        //查询一个
        List<Account> accounts = jt.query("select * from account where id = ?",new BeanPropertyRowMapper<Account>(Account.class),1);
        System.out.println(accounts.isEmpty()?"没有内容":accounts.get(0));

        //查询返回一行一列（使用聚合函数，但不加group by子句）
        Long count = jt.queryForObject("select count(*) from account where money > ?",Long.class,1000f);
        System.out.println(count);

//如何自己实现RowMapper接口
class AccountRowMapper implements RowMapper<Account>{
    //把结果集中的数据封装到Account中，然后由spring把每个Account加到集合中
    public Account mapRow(ResultSet resultSet, int i) throws SQLException {
        Account account = new Account();
        account.setId(resultSet.getInt("id"));
        account.setName(resultSet.getString("name"));
        account.setMoney(resultSet.getFloat("money"));
        return account;
    }
}

在Dao中使用JdbcTemplate

首先添加配置文件

<?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.xsd">

    <!-- 配置账户的持久层-->
    <bean id="accountDao" class="com.mantishell.dao.impl.AccountDaoImpl">
        <property name="jdbcTemplate" ref="jdbcTemplate"></property>
    </bean>

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

    <!-- 配置数据源-->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
        <property name="url" value="jdbc:mysql://localhost:3306/db4"></property>
        <property name="username" value="root"></property>
        <property name="password" value="123456"></property>
    </bean>
</beans>

添加dao的接口，以及实现类

public interface IAccountDao {
    Account findAccountById(Integer accountId);
    Account findAccountByName(String accountName);
    void updateAccount(Account account);
}

public class AccountDaoImpl implements IAccountDao {

    private JdbcTemplate jdbcTemplate;
    
    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    public Account findAccountById(Integer accountId) {
        List<Account> accounts = jdbcTemplate.query("select * from account where id = ?",new BeanPropertyRowMapper<Account>(Account.class),accountId);
        return accounts.isEmpty()?null:accounts.get(0);
    }

    public Account findAccountByName(String accountName) {
        List<Account> accounts = jdbcTemplate.query("select * from account where name = ?",new BeanPropertyRowMapper<Account>(Account.class),accountName);
        if(accounts.isEmpty()){
            return null;
        }
        if(accounts.size()>1){
            throw new RuntimeException("结果集不唯一");
        }
        return accounts.get(0);
    }

    public void updateAccount(Account account) {
        jdbcTemplate.update("update account set name=?,money=? where id=?",account.getName(),account.getMoney(),account.getId());
    }
}    

测试：

    public static void main(String[] args) {
        //1、获取容器
        ApplicationContext ac = new ClassPathXmlApplicationContext("bean.xml");
        //2、获取对象
        IAccountDao accountDao = ac.getBean("accountDao", IAccountDao.class);

        Account account = accountDao.findAccountById(1);
        System.out.println(account);
        
        account.setMoney(100f);
        accountDao.updateAccount(account);
    }