Sping使用Jdbc Template

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1. 概述

SpringJdbcTemplate是spring框架中提供的一个对象，是对原始JDBC API对象的简单封装。spring框架为我们提供了很多的操作模板类。

• 操作关系型数据的：JdbcTemplate、HibernateTemplate
• 操作nosql数据库的：RedisTemplate
• 操作消息队列的：JmsTemplate

2. 环境配置

• 导入坐标

<dependency>
    <groupId>org.springframeworkgroupId>
    <artifactId>spring-jdbcartifactId>
    <version>5.0.2.RELEASEversion>
dependency>

• bean.xml配置文件中添加约束：

<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">
beans>

3. XML配置使用

3.1 直接使用

直接通过new的方式获取JdbcTemplate对象，并使用其中的query()实现查询所有或者根据具体条件查询；使用update()执行保存、更新、删除操作；使用queryforObject()使用SQL中的聚合函数执行查询……

public class JdbcTemplateDemo1 {
    public static void main(String[] args) {
        DriverManagerDataSource ds = new DriverManagerDataSource();
        ds.setDriverClassName("com.mysql.cj.jdbc.Driver");
        ds.setUrl("jdbc:mysql://localhost:3306/sql_store?serverTimezone=GMT");
        ds.setUsername("root");
        ds.setPassword("1234");

        JdbcTemplate jt = new JdbcTemplate();
        jt.setDataSource(ds);

        // 查询所有
        List<Account> accounts = jt.query("select * from account where money = ?",new BeanPropertyRowMapper<Account>(Account.class),1000f);
        for(Account account : accounts){
            System.out.println(account);
        }

        // 保存
        jt.update("insert into account(name,money)values(?,?)","Ball",1000f);

        // 更新
        jt.update("update account set name=?,money=? where id=?","Amy", 2000, 1);

        // 删除
        jt.update("delete from account where id=?",1);

        // 查询一个
        List<Account> accounts1 = jt.query("select * from account where id = ?",new BeanPropertyRowMapper<Account>(Account.class),1);
        System.out.println(accounts.isEmpty()?"没有内容":accounts1.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);
    }
}

3.2 配置使用

account表中的内容如下：

mysql> select * from account;
+----+----------+-------+
| id | name     | money |
+----+----------+-------+
|  1 | Forlogen |  1000 |
|  2 | Kobe     |  1000 |
|  3 | James    |  1000 |
+----+----------+-------+
3 rows in set (0.00 sec)

创建实体类：

public class Account implements Serializable {

    private Integer id;
    private String name;
    private Float money;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Float getMoney() {
        return money;
    }

    public void setMoney(Float money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", money=" + money +
                '}';
    }
}

创建持久层接口：

public interface IAccountDao {

    Account findAccountById(Integer accountId);

    Account findAccountByName(String accountName);

    void updateAccount(Account account);
}

创建接口的实现类，并继承JdbcSupport。此时执行查询等操作时调用的方法所需参数是不同的：

public class IAccountDaoImpl1 extends JdbcSupport implements IAccountDao {
    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    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);
    }

    @Override
    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);
    }

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

JdbcSupport自定义如下：

public class JdbcSupport {
    private JdbcTemplate jdbcTemplate;

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

    public JdbcTemplate getJdbcTemplate() {
        return jdbcTemplate;
    }

    public void setDataSource(DataSource dataSource) {
        if(jdbcTemplate == null){
            jdbcTemplate = createJdbcTemplate(dataSource);
        }
    }

    private JdbcTemplate createJdbcTemplate(DataSource dataSource){
        return new JdbcTemplate(dataSource);
    }
}

创建bean.xml文件，在容器中注入JdbcTemplate：

<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">

    <bean id="accountDao" class="dyliang.dao.impl.IAccountDaoImpl1">
        <property name="jdbcTemplate" ref="jdbcTemplate">property>
    bean>

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

    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver">property>
        <property name="Url" value="jdbc:mysql://localhost:3306/sql_store?serverTimezone=GMT">property>
        <property name="username" value="root">property>
        <property name="password" value="1234">property>
    bean>
beans>

最后获取JdbcTemplate对象，调用query()实现查询功能：

public class JdbcTempalteDemo2 {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("bean.xml");
        JdbcTemplate jt = ac.getBean("jdbcTemplate",JdbcTemplate.class);
        
        List<Account> accounts = jt.query("select * from account where money = ?",new BeanPropertyRowMapper<Account>(Account.class),1000f);
        for(Account account : accounts){
            System.out.println(account);
        }
    }
}

Account{id=1, name='Forlogen', money=1000.0}
Account{id=2, name='Kobe', money=1000.0}
Account{id=3, name='James', money=1000.0}

或者通过accountDao直接调用持久层接口实现类中的方法：

public class JdbcTemplateDemo3 {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("bean.xml");
        IAccountDao accountDao = ac.getBean("accountDao", IAccountDao.class);

        Account accountById = accountDao.findAccountById(1);
        System.out.println(accountById);
    }
}

Account{id=1, name='Forlogen', money=1000.0}