java：Spring JDBC Template

concept

A simple encapsulation of JDBC by the Spring framework. A JDBCTemplate object is provided to simplify the development of JDBC.

step

1. import jar package
2. Create a JdbcTemplate object. Depends on the data source DataSource
   • JdbcTemplate template = new JdbcTemplate(ds);
3. Call the method of JdbcTemplate to complete the CRUD operation
   • update(): Execute DML statements. add, delete, change statement
   • queryForMap(): The query result encapsulates the result set as a map collection, uses the column name as the key, and uses the value as the value to encapsulate this record as a map collection
     • Note: The result set length of this method query can only be 1
   • queryForList(): The query result encapsulates the result set as a list collection
     • Note: Encapsulate each record into a Map collection, and then load the Map collection into the List collection
   • query(): Query results, encapsulate the results as JavaBean objects
     • query parameters: RowMapper
       • Generally we use the BeanPropertyRowMapper implementation class. Can complete the automatic encapsulation of data to JavaBean
       • new BeanPropertyRowMapper<type>(type.class)
   • queryForObject: Query results, encapsulate the results as objects
     • Generally used for aggregate function queries

example

package cn.xxx.jdbctemplate;

import cn.xxx.utils.JDBCUtils;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * JdbcTemplate入门
 */
public class JdbcTemplateDemo1 {
    
    

    public static void main(String[] args) {
    
    
        //1.导入jar包
        //2.创建JDBCTemplate对象
        JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
        //3.调用方法
        String sql = "update account set balance = 5000 where id = ?";
        int count = template.update(sql, 3);
        System.out.println(count);
    }
}

Unit test all APIs

1. Modify the salary of No. 1 data to 10000
2. add a record
3. Delete the record just added
4. Query the record whose id is 1 and encapsulate it as a Map collection
5. Query all records and encapsulate it as a List
6. Query all records and encapsulate them as a List collection of Emp objects
7. Query the total number of records

package cn.xxx.jdbctemplate;

import cn.xxx.domain.Emp;
import cn.xxx.utils.JDBCUtils;
import org.junit.Test;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

import java.sql.Date;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;

public class JdbcTemplateDemo2 {
    
    

    //Junit单元测试，可以让方法独立执行


    //1. 获取JDBCTemplate对象
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
    /**
     * 1. 修改1号数据的 salary 为 10000
     */
    @Test
    public void test1(){
    
    

        //2. 定义sql
        String sql = "update emp set salary = 10000 where id = 1001";
        //3. 执行sql
        int count = template.update(sql);
        System.out.println(count);
    }

    /**
     * 2. 添加一条记录
     */
    @Test
    public void test2(){
    
    
        String sql = "insert into emp(id,ename,dept_id) values(?,?,?)";
        int count = template.update(sql, 1015, "郭靖", 10);
        System.out.println(count);

    }

    /**
     * 3.删除刚才添加的记录
     */
    @Test
    public void test3(){
    
    
        String sql = "delete from emp where id = ?";
        int count = template.update(sql, 1015);
        System.out.println(count);
    }

    /**
     * 4.查询id为1001的记录，将其封装为Map集合
     * 注意：这个方法查询的结果集长度只能是1
     */
    @Test
    public void test4(){
    
    
        String sql = "select * from emp where id = ? or id = ?";
        Map<String, Object> map = template.queryForMap(sql, 1001,1002);
        System.out.println(map);
        //{id=1001, ename=孙悟空, job_id=4, mgr=1004, joindate=2000-12-17, salary=10000.00, bonus=null, dept_id=20}

    }

    /**
     * 5. 查询所有记录，将其封装为List
     */
    @Test
    public void test5(){
    
    
        String sql = "select * from emp";
        List<Map<String, Object>> list = template.queryForList(sql);

        for (Map<String, Object> stringObjectMap : list) {
    
    
            System.out.println(stringObjectMap);
        }
    }

    /**
     * 6. 查询所有记录，将其封装为Emp对象的List集合
     */

    @Test
    public void test6(){
    
    
        String sql = "select * from emp";
        List<Emp> list = template.query(sql, new RowMapper<Emp>() {
    
    

            @Override
            public Emp mapRow(ResultSet rs, int i) throws SQLException {
    
    
                Emp emp = new Emp();
                int id = rs.getInt("id");
                String ename = rs.getString("ename");
                int job_id = rs.getInt("job_id");
                int mgr = rs.getInt("mgr");
                Date joindate = rs.getDate("joindate");
                double salary = rs.getDouble("salary");
                double bonus = rs.getDouble("bonus");
                int dept_id = rs.getInt("dept_id");

                emp.setId(id);
                emp.setEname(ename);
                emp.setJob_id(job_id);
                emp.setMgr(mgr);
                emp.setJoindate(joindate);
                emp.setSalary(salary);
                emp.setBonus(bonus);
                emp.setDept_id(dept_id);

                return emp;
            }
        });


        for (Emp emp : list) {
    
    
            System.out.println(emp);
        }
    }

    /**
     * 6. 查询所有记录，将其封装为Emp对象的List集合
     */

    @Test
    public void test6_2(){
    
    
        String sql = "select * from emp";
        List<Emp> list = template.query(sql, new BeanPropertyRowMapper<Emp>(Emp.class));
        for (Emp emp : list) {
    
    
            System.out.println(emp);
        }
    }

    /**
     * 7. 查询总记录数
     */

    @Test
    public void test7(){
    
    
        String sql = "select count(id) from emp";
        Long total = template.queryForObject(sql, Long.class);
        System.out.println(total);
    }

}