2020-08-17Spring jdbc

Spring jdbc

• 概念
  Spring框架对JDBC的简单封装，提供了一个JDBCTemplate对象简化JDBC的开发
• 步骤

1. 导入jar包
2. 创建对象JdbcTemplate，依赖于数据源DataSource(数据库连接池)
   JdbcTemplate template = new JdbcTemplate(datasource)
3. 调用JdbcTemplate的方法来完成CRUD的操作
   ①update()：执行DML（增删改）
   ②queryForMap()：查询结果将结果封装为map集合
   注意：这个方法查询到结果集长度只能为1，将列名作为key，将值作为value
   ③queryForList()：查询结果将结果封装为list集合
   注意：将每条记录封装为map集合，再将Map集合装载到List集合中
   ④query()：查询结果，将结果封装为JavaBean对象
   注意：query的参数RowMapper：一般我们使用 new BeanPropertyRowMapper<类>(类.class).可以完成数据到javabean的自动封装;还可以使用new RowMapper(){}重写mapRow方法
   ⑤queryForObject()：查询结果，将结果封装为对象
   注意：一般用于集合函数的查询。queryForObject(sql, 值的类型.class);

package it.heima;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.junit.Test;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

import javax.sql.DataSource;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import java.util.Properties;

public class springJdbcTest {
    public static JdbcTemplate getjdbcTemplate(){
        //1.获得datasource
        DataSource dataSource = null;
        Properties properties = new Properties();
        ClassLoader classLoader = springJdbcTest.class.getClassLoader();
        URL springJdbcTest = classLoader.getResource("druid.properties");
        String path = springJdbcTest.getPath();
        try {
            properties.load(new FileReader(path));
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            e.printStackTrace();
        }
        //2.创建JDBCTemplate对象
        JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
        return jdbcTemplate;
    }
    @org.junit.Test
    public void update(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        //更新数据
        String sql = "update student set name='duyanju' where id = ?";
        int update = jdbcTemplate.update(sql, 3);
        System.out.println(update);
    }
    @Test
    public void insert(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "insert into student (id,name,cid) values(?,?,?)";
        int xiaoming = jdbcTemplate.update(sql, 4, "xiaoming", 1);
        System.out.println(xiaoming);
    }
    @Test
    public void delete(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "delete from student where id = ?";
        int update = jdbcTemplate.update(sql,2);
        System.out.println(update);
    }
    /*
     *queryFormap这个方法查询的结果长度只能为1
     */
    @Test
    public void queryFormap(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "select t1.id,t1.name,t2.name as cname from student t1,class t2 where t1.cid=t2.cid and t1.id=1";
        Map stringObjectMap = jdbcTemplate.queryForMap(sql);
        System.out.println(stringObjectMap);
        //{id=1, name=小明, cname=高二1班}
    }
    /*
    将每条记录封装为map集合，再将Map集合装载到List集合中
     */
    @Test
    public void queryForlist(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "select t1.id,t1.name,t2.name as cname from student t1,class t2 where t1.cid=t2.cid";
        List> maps = jdbcTemplate.queryForList(sql);
        System.out.println(maps);
        //[{id=1, name=小明, cname=高二1班}, {id=3, name=duyanju, cname=高一2班}, {id=4, name=xiaoming, cname=高二1班}]
    }
    /*
    * 将其封装为对象，再装载到list集合中
    * */
    @Test
    public void query(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "select t1.id,t1.name,t2.name as cname from student t1,class t2 where t1.cid=t2.cid";
        //匿名内部类
        List list = jdbcTemplate.query(sql, new RowMapper() {
            @Override
            public Student mapRow(ResultSet resultSet, int i) throws SQLException {
                Student student = new Student();
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String cname = resultSet.getString("cname");
                student.setId(id);
                student.setName(name);
                student.setClassname(cname);
                return student;
            }
        });
        System.out.println(list);
        //[Student{id=1, name='小明', classname='高二1班'}, Student{id=3, name='duyanju', classname='高一2班'}, Student{id=4, name='xiaoming', classname='高二1班'}]
    }
    @Test
    public void query1(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "select t1.id,t1.name,t2.name as cname from student t1,class t2 where t1.cid=t2.cid";
        //匿名内部类
        List list = jdbcTemplate.query(sql, new BeanPropertyRowMapper(Student.class));
        System.out.println(list);
        //[Student{id=1, name='小明', classname='高二1班'}, Student{id=3, name='duyanju', classname='高一2班'}, Student{id=4, name='xiaoming', classname='高二1班'}]
    }
    /*
    *查询总记录数
     */
    @Test
    public void queryForObject(){
        JdbcTemplate jdbcTemplate = getjdbcTemplate();
        String sql = "select count(id) from student";
        Integer integer = jdbcTemplate.queryForObject(sql, Integer.class);
        System.out.println(integer);
        //3
    }
}

工具类