dbUtil的更新和查询

一、代码设计：

******************************实体类设计********************************

package dbutil;
/*
* 实体类设计
*/
public class Admin {
//属性
private int id;
private String userName;
private String pwd;

/**
* @return the id
*/
public int getId() {
  return id;
}
/**
* @param id the id to set
*/
public void setId(int id) {
  this.id = id;
}
/**
* @return the userName
*/
public String getUserName() {
  return userName;
}
/**
* @param userName the userName to set
*/
public void setUserName(String userName) {
  this.userName = userName;
}
/**
* @return the pwd
*/
public String getPwd() {
  return pwd;
}
/**
* @param pwd the pwd to set
*/
public void setPwd(String pwd) {
  this.pwd = pwd;
}

@Override
public String toString() {
  return "admin[id = "+id+",userName = "+userName+",pwd = "+pwd+"]";
}
}

***********************************dbUtil组件**********************************************

package dbutil;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.junit.Test;

public class App {

/* 使用dbutil组件更新*/
@Test
public void testUpdate() throws Exception{
  //1.语句
  String sql = "delete from admin where id = 27";
  //2.连接数据库
  Connection conn = JdbcUtil.getConnection();
  //3.dbutil核心工具类
  QueryRunner qr = new QueryRunner();
  //4.执行
  qr.update(conn, sql);
}
/*
* 使用dbutil组件查询
*/
@Test
public void testQuery() throws Exception{
  String sql = "select * from admin";
  //1.连接数据库
  Connection conn = JdbcUtil.getConnection();
  //2.创建核心工具类
  QueryRunner qr = new QueryRunner();
  //3.执行
  List<Admin> list = qr.query(conn, sql, new BeanListHandler<Admin>(Admin.class));

  //4.输出结果
  for(int i = 0; i < list.size(); i++){
   System.out.println(list.get(i));
  }
  conn.close();
}
}

**********************************************jdbc**********************************************

package dbutil;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JdbcUtil {

//第一种方法： private String url = "jdbc:mysql://localhost:3306/day17";
private static String url = "jdbc:mysql:///day17";//第二种方法
private static String user = "root";
private static String password = "root";

//写成静态方法，用类名.getConnection()获取该连接对象
public static Connection getConnection() {
  try {
   Class.forName("com.mysql.jdbc.Driver");
   return DriverManager.getConnection(url, user, password);
  } catch (Exception e) {
   throw new RuntimeException(e);
  }
}

/**
* 关闭
* 关闭原则：后开先关
*/
public static void closeAll(Connection con, Statement stmt, ResultSet rs) {
  try {
   if (rs != null) {
    rs.close();
    rs = null;   // 建议释放资源
   }
   if (stmt != null) {
    stmt.close();
    stmt = null;
   }
   if (con != null && !con.isClosed()) {
    con.close();
    con = null;
   }
  } catch (SQLException e) {
   throw new RuntimeException(e);
  }
}
}

二、运行结果（1.删除数据库day17admin 表中id为27的数据 2.把数据库day17中的admin表中的数据全部输出）：

dbUtil的更新和查询

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