数据库开发四：JDBC数据库开发进阶三(commons-dbutils原理)

自定义封装泛型工具类

package dbutils;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * 封装泛型工具类
 * Created by kevin on 2020/4/2.
 */
public class QR<T> {
    private DataSource dataSource;

    public QR() {
        super();
    }

    public QR(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    /**
     * 增删改
     * @param sql
     * @param parms
     * @return
     */
    public int update(String sql,Object...parms){
        Connection connection = null;
        PreparedStatement pstmt = null;
        try {
            connection = dataSource.getConnection();
            pstmt = connection.prepareStatement(sql);
            initParams(pstmt,parms);
            return pstmt.executeUpdate();
        } catch (SQLException e) {
           throw new RuntimeException(e);
        } finally {
            try {
                if(pstmt!=null){
                    pstmt.close();
                }
                if(connection!=null){
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    private void initParams(PreparedStatement pstmt,Object...parms){
        try {
            for(int i=0;i<parms.length;i++){
                pstmt.setObject(i+1,parms[i]);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

    /**
     * 查询单个对象
     * @param sql
     * @param rh
     * @param parms
     * @return
     */
    public T query(String sql,RsHandler<T> rh,Object...parms){
        Connection connection = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            connection = dataSource.getConnection();
            pstmt = connection.prepareStatement(sql);
            initParams(pstmt,parms);
            rs = pstmt.executeQuery();
            return rh.handle(rs);
        } catch (SQLException e) {
           throw new RuntimeException(e);
        } finally {
            try {
                if(pstmt!=null){
                    pstmt.close();
                }
                if(rs!=null){
                    rs.close();
                }
                if(connection!=null){
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

/**
 * 处理对象映射
 * @param <T>
 */
interface RsHandler<T>{
    public T handle(ResultSet rs) throws SQLException;
}

自定义调用

package dbutils;

import org.junit.Test;

import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * 仿commons-dbutils
 * Created by kevin on 2020/4/2.
 */
public class Demo2 {
    @Test
    public void fun1(){
//        Stu stu = new Stu();
//        stu.setNumber("0002");
//        stu.setName("王五");
//        stu.setAge(30);
//        stu.setGender("男");
//        stu.setPassword("111111");
//        add(stu);

        Stu stu2 = load("0002");
        System.out.println(stu2.toString());
    }

    public int add(Stu stu){
        QR<Stu> stuQr = new QR<Stu>(JdbcUtils.getDataSource());
        String sql="insert into stu values(?,?,?,?,?)";
        Object[] params = {stu.getNumber(),stu.getName(),stu.getAge(),stu.getGender(),stu.getPassword()};
        return stuQr.update(sql,params);
    }

    public Stu load(String number){
        QR<Stu> stuQr = new QR<Stu>(JdbcUtils.getDataSource());
        String sql="select * from stu where number=?";
        Object[] params = {number};
        RsHandler<Stu> rh = new RsHandler<Stu>() {
            @Override
            public Stu handle(ResultSet rs) throws SQLException{
                if(!rs.next())  return null;
                Stu stu = new Stu();
                stu.setNumber(rs.getString("number"));
                stu.setName(rs.getString("name"));
                stu.setAge(rs.getInt("age"));
                stu.setGender(rs.getString("gender"));
                stu.setPassword(rs.getString("password"));
                return stu;
            }
        };
        return stuQr.query(sql,rh,params);
    }
}

使用commons-dbutils

package dbutils;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.junit.Test;

import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * commons dbutils
 * Created by kevin on 2020/4/2.
 */
public class Demo3 {
    @Test
    public void fun1(){
       QueryRunner qr= new QueryRunner(JdbcUtils.getDataSource());
        String sql="insert into stu values(?,?,?,?,?)";
        Object[] params = {"0003","李四",30,"男","111111"};
        try {
            qr.update(sql,params);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Test
    public void fun2(){
        QueryRunner qr= new QueryRunner(JdbcUtils.getDataSource());
        String sql="select * from stu where number=?";
        Object[] params = {"0003"};
        try {
//            ResultSetHandler<Stu> handler = new ResultSetHandler<Stu>() {
//                @Override
//                public Stu handle(ResultSet rs) throws SQLException {
//                    if(!rs.next())  return null;
//                    Stu stu = new Stu();
//                    stu.setNumber(rs.getString("number"));
//                    stu.setName(rs.getString("name"));
//                    stu.setAge(rs.getInt("age"));
//                    stu.setGender(rs.getString("gender"));
//                    stu.setPassword(rs.getString("password"));
//                    return stu;
//                }
//            };//该部分代码commons-dbutils已经有5个实现类了可以直接调用
            //BeanHandler类是ResultSetHandler实现类,BeanHandler类使用需知(数据库列名必须与实体类名称相同)
            BeanHandler<Stu> beanHandler = new BeanHandler<Stu>(Stu.class);
            Stu stu = qr.query(sql,beanHandler,params);
            System.out.println(stu.toString());
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}