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JDBC基础学习之增删改查(3)

发布时间:2010-05-20 14:01:29 文章来源:www.iduyao.cn 采编人员:星星草
JDBC基础学习之增删改查(三)

一、准备工作,创建表人员信息表(t_person)、用户表(user)、机构信息表(t_org)

sql脚本:

/*
Navicat MySQL Data Transfer

Source Server         : localhost
Source Server Version : 50162
Source Host           : localhost:3306
Source Database       : demo

Target Server Type    : MYSQL
Target Server Version : 50162
File Encoding         : 65001

Date: 2017-12-02 10:07:32
*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for t_org
-- ----------------------------
DROP TABLE IF EXISTS `t_org`;
CREATE TABLE `t_org` (
  `id` int(4) NOT NULL AUTO_INCREMENT,
  `pid` int(4) DEFAULT NULL,
  `name` varchar(100) NOT NULL,
  `description` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of t_org
-- ----------------------------
INSERT INTO `t_org` VALUES ('1', '0', '实施组', '调研、实施');
INSERT INTO `t_org` VALUES ('2', '0', '开发组', '开发');
INSERT INTO `t_org` VALUES ('3', '0', '财务部', '做账、');
INSERT INTO `t_org` VALUES ('4', '0', '人力资源部', '人力资源');

-- ----------------------------
-- Table structure for t_person
-- ----------------------------
DROP TABLE IF EXISTS `t_person`;
CREATE TABLE `t_person` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `oid` int(4) DEFAULT NULL,
  `name` varchar(100) NOT NULL,
  `sex` char(1) NOT NULL,
  `address` varchar(200) DEFAULT NULL,
  `age` int(4) DEFAULT NULL,
  `phone` varchar(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of t_person
-- ----------------------------
INSERT INTO `t_person` VALUES ('1', '1', '张三', '1', 'xxxxx', '20', '13984848326');
INSERT INTO `t_person` VALUES ('2', '1', '张飞', '1', 'xxxxx', '22', '10086');
INSERT INTO `t_person` VALUES ('3', '2', '杨过', '1', 'xxxxx', '25', '10000');
INSERT INTO `t_person` VALUES ('4', '3', '小龙女', '0', 'xxxxx', '25', '10086');

-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(4) NOT NULL,
  `pid` int(11) DEFAULT NULL,
  `user_name` varchar(50) NOT NULL,
  `password` varchar(50) DEFAULT NULL,
  `create_time` bigint(20) DEFAULT NULL,
  `expired_time` bigint(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES ('1', '1', 'zhangsan', '123456', null, null);
INSERT INTO `user` VALUES ('2', '2', 'zhangfei', '123456', null, null);
INSERT INTO `user` VALUES ('3', '3', 'yangguo', '123456', null, null);
INSERT INTO `user` VALUES ('4', '4', 'xiaolongnv', '123456', null, null);

 二、查询出人员表中的所有信息

public class Test {

	public static void main(String[] args) {
		Connection conn = null;
		String url = "jdbc:mysql://127.0.0.1:3306/demo";
		String user = "root";
		String password = "root_123";
		ResultSet rs = null;
		Statement stmt = null;
		try {
			// 第一步:加载驱动
			Class.forName("com.mysql.jdbc.Driver");
			// 第二步:得到链接
			conn = DriverManager.getConnection(url, user, password);
			//第三步:创建执行SQL语句的statement
			stmt = conn.createStatement();
			String sql = "select * from t_person";
			//第四步:处理执行的结果
			rs = stmt.executeQuery(sql);
			while (rs.next()) {
				StringBuffer sb = new StringBuffer();
				sb.append("id:" + rs.getInt("id") + "t")
				  .append("name:" + rs.getString("name")  + "t")
				  .append("address:" + rs.getString("address")  + "t")
				  .append("sex:" + rs.getString("sex")  + "t")
				  .append("age:" + rs.getInt("age")  + "t")
				  .append("phone:" + rs.getString("phone")  + "t");
				System.out.println(sb.toString());
			}

		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			//第五步:释放资源
			if(null != rs){
				try {
					rs.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(null != stmt){
				try {
					stmt.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(null != conn){
				try {
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
	}

}

三、创建表t_test

 

public class Test2 {

	public static void main(String[] args) {
		Connection conn = null;
		Statement stmt = null;
		String url = "jdbc:mysql://127.0.0.1:3306/demo";
		String user = "root";
		String password = "root_123";
		try {
			//第一步:加载驱动
			Class.forName("com.mysql.jdbc.Driver");
			//第二步:得到链接
			conn = DriverManager.getConnection(url, user, password);
			//第三步:创建执行SQL的statement语句
			stmt = conn.createStatement();
			StringBuffer sbSql = new StringBuffer();
			sbSql.append("create table t_test( ")
				 .append("id int(4) primary key not null, ")
				 .append("user_name varchar (20) not null ")
				 .append(");");
			stmt.executeUpdate(sbSql.toString());
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			//第四步:释放资源
			if(null != stmt){
				try {
					stmt.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(null != conn){
				try {
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

 思考:举一反三,大家可以尝试下删除、修改之类的操作。

四、连接数据库的工具类DBUtil

 

由于对数据库常见的操作是CRUD,并且进行操作时基本的步骤都相似,因此我们把数据库的连接和资源的关闭进行封装.

 

package com.zlt.jdbc.util;

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

/**
 * 将数据库的连接以及资源的释放封装成一个通用的工具类
 * 
 * @author 涛声一笑 289836653
 *
 */
public class DBUtil {

	/**
	 * 得到数据库连接
	 * @return
	 */
	public static Connection getConnection() {
		Connection conn = null;
		String url = "jdbc:mysql://127.0.0.1:3306/demo";
		String user = "root";
		String password = "root_123";
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(url, user, password);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}

	/**
	 * 释放结果集资源
	 * @param rs
	 */
	public static void close(ResultSet rs){
		if(null != rs) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
	
	/**
	 * 释放执行SQL的statement资源
	 * @param stmt
	 */
	public static void close(Statement stmt){
		if(null != stmt) {
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		} 
	}
	
	
	/**
	 * 释放数据库连接Connection
	 * @param conn
	 */
	public static void close(Connection conn){
		if(null != conn) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
}

 单元测试

package com.zlt.jdbc.util;

import junit.framework.TestCase;

public class DBUtilTest extends TestCase {
	protected void setUp() throws Exception {
		super.setUp();
	}
	public void testGetConnection() {
		System.out.println(DBUtil.getConnection());
	}
}

 五、将查询的结果与JAVA对象模型联系起来

         5.1建立对象模型(JavaBean)

package com.zlt.jdbc;

/**
 * 建立关系模型与对象模型之间的映射
 * 对象模型实体Person与关系模型t_person(暂不考虑关系与关系之间的关联)
 * @author 涛声一笑  289836653
 *
 */
public class Person {
	
	private int id;
	private int oid;
	private String name;
	private String sex;
	private String address;
	private int age;
	private String phone;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public int getOid() {
		return oid;
	}
	public void setOid(int oid) {
		this.oid = oid;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getPhone() {
		return phone;
	}
	public void setPhone(String phone) {
		this.phone = phone;
	}		
}

 

    5.2根据人员ID查询出人员信息

package com.zlt.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import com.zlt.jdbc.util.DBUtil;

public class Test3 {

	public static void main(String[] args) {
		Person p = findPersonById(1);
		System.out.println("id:" + p.getId() +"name:" +p.getName() + "age:" + p.getAge() + "sex:" + p.getSex() + "oid:" + p.getOid() + "address:" + p.getAddress() +"phone:" + p.getPhone());
	}
	
	/**
	 * 根据人员ID查询出人员的信息
	 * (建议平时写代码时先把SQL语句调通)
	 * select id,oid,name,sex,age,address,phone from t_person
	 * @param id 人员ID
	 * @return p,p为null时表示没查询到 
	 */
	public static Person findPersonById(int id){
		Person p = null;
		Connection conn = null;
		Statement stmt = null;
		ResultSet rs = null;
		try {
			conn  = DBUtil.getConnection();
			stmt = conn.createStatement();
			String sql = "select id,oid,name,sex,age,address,phone from t_person";
			rs = stmt.executeQuery(sql);
			if(rs.next()) {
				p = new Person();
				p.setId(rs.getInt("id"));
				p.setName(rs.getString("name"));
				p.setOid(rs.getInt("oid"));
				p.setSex(rs.getString("sex"));
				p.setAge(rs.getInt("age"));
				p.setAddress(rs.getString("address"));
				p.setPhone(rs.getString("phone"));
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			DBUtil.close(stmt);
			DBUtil.close(rs);
			DBUtil.close(conn);
		}
		return p;
	}
}

    5.3查询出姓名为张姓的人员信息

public static List<Person> findPersonByName(String name){
		Connection conn = null;
		Statement stmt = null;
		ResultSet rs = null;
		List<Person> persons = new ArrayList<Person>();
		try {
			conn  = DBUtil.getConnection();
			stmt = conn.createStatement();
			String sql = "select id,oid,name,sex,age,address,phone from t_person where name like '%"+name+"%'";
			rs = stmt.executeQuery(sql);
			while(rs.next()) {
				Person p = new Person();
				p.setId(rs.getInt("id"));
				p.setName(rs.getString("name"));
				p.setOid(rs.getInt("oid"));
				p.setSex(rs.getString("sex"));
				p.setAge(rs.getInt("age"));
				p.setAddress(rs.getString("address"));
				p.setPhone(rs.getString("phone"));
				persons.add(p);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			DBUtil.close(stmt);
			DBUtil.close(rs);
			DBUtil.close(conn);
		}
		return persons;
	}

    5.4遗留问题:此时使用Statement执行SQL语句时进行拼串,使用该种语句有两个缺点1)有SQL注入问题 2)当控制条件越多,拼串难度越繁琐

写道
推荐使用PreparedStatement语句,其有效的防止sql注入(SQL语句在程序运行前已经进行了预编译,当运行时动态地把参数传给PreprareStatement时,即使参数里有敏感字符如 or '1=1'也数据库会作为一个参数一个字段的属性值来处理而不会作为一个SQL指令

    5.5使用PrepareStatement语句重写b示例,但是在重写c示例时,发现模糊查询查不出结果但程序没错,因此一般情况下推荐使用P repareStatement,但有时必须使用Statement进行拼串

public static Person findPersonById(int id){
		Person p = null;
		Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			conn  = DBUtil.getConnection();
			String sql = "select id,oid,name,sex,age,address,phone from t_person where id = ?" ;
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			rs = pstmt.executeQuery();
			if(rs.next()) {
				p = new Person();
				p.setId(rs.getInt("id"));
				p.setName(rs.getString("name"));
				p.setOid(rs.getInt("oid"));
				p.setSex(rs.getString("sex"));
				p.setAge(rs.getInt("age"));
				p.setAddress(rs.getString("address"));
				p.setPhone(rs.getString("phone"));
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			DBUtil.close(pstmt);
			DBUtil.close(rs);
			DBUtil.close(conn);
		}
		return p;
	}

   举一反三:

写道
1)查询人员编号为1,3,5的人员信息。
2)查询年龄在20-25之间的人员信息
3)将姓名为小龙女的人的住址、电话分别更新为绝情谷底,10008611
4)往人员信息表中插入一位新人员(5,3,周伯通,1,30,四海为家,10086)
5)将张三和张飞两个人从表中删除
6)查询姓名为杨过的用户信息以及人员信息

 

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