java JDBC 连接数据库（增删查改）

必须先插入工具包

代码

 public static void main(String[] args) {
        DataSource ds = JdbcHelper.getDs();
        System.out.println(ds);
        JdbcTemplate jdbcTemplate=new JdbcTemplate(ds);
        System.out.println(jdbcTemplate);
        //新增
        String sql1="insert into biao values(null,?,?,?)";
        int i=jdbcTemplate.update(sql1,"6",6,"6");
        System.out.println(i);
        //删除
        String sql2="delete from biao where id=?";
        int a=jdbcTemplate.update(sql2,"2");
        System.out.println(a);
        //修改
        String sql3="update  biao set name=? where id=2";
        int b=jdbcTemplate.update(sql3,"小军");
        System.out.println(b);
        //查询单个数据
        String sql4="select *from biao where id=?";
        Map<String, Object> stringObjectMap = jdbcTemplate.queryForMap(sql4,3);
        System.out.println(stringObjectMap);
        //查询多个数据
        String sql5="select * from biao where id>?";
        List<Map<String, Object>> maps = jdbcTemplate.queryForList(sql5, 5);
        System.out.println(maps);

        String sql6="select id(3) from biao where age>?";
        String s = jdbcTemplate.queryForObject(sql6, String.class, 20);
        System.out.println(s);
    }

！！！查询！！！

![在这里插入图片描述](https://img-blog.csdnimg.cn/direct/0e9185bf852740c584658d608c3101af.png

查询

 public static void main(String[] args) {
        DataSource ds = JdbcHelper.getDs();
        System.out.println(ds);
        JdbcTemplate jdbcTemplate=new JdbcTemplate(ds);
        System.out.println(jdbcTemplate);
        String sql="select * from biao where id>?";
        BeanPropertyRowMapper<Test2>  rowMapper=new BeanPropertyRowMapper<>(Test2.class);
        List<Test2> query=jdbcTemplate.query(sql,rowMapper,5);
        System.out.println(query);
        for(Test2 bean:query){
            System.out.println(bean);
            int id = bean.getId();
            System.out.println(id);
        }
    }

运行结果