Java后端开发——JDBC组件
JDBC（Java Database Connectivity）是Java SE平台的一种标准API，它提供了一种标准的方法来访问关系型数据库，使得Java程序能够与各种不同的数据库进行交互，这篇文章我们来进行实验体验一下。
自定义JDBC连接工具类
1.编写第一代JDBCUtils并测试查看结果
第一代JDBCUtils：
package com.javaweb.utils;
import java.io.FileReader;
import java.sql.*;
import java.util.Properties;
public class JDBCUtils2 {
private static String driver;
private static String url;
private static String user;
private static String password;
static {
try {
// 1. 创建Properties集合类。
Properties properties = new Properties();
// 2. 加载文件
properties.load(new FileReader(JDBCUtils.class.getClassLoader().getResource("jdbc.properties").getPath()));
driver = properties.getProperty("driver");
url = properties.getProperty("url");
user = properties.getProperty("user");
password = properties.getProperty("password");
// 注册驱动
Class.forName(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, user, password);
}
// 释放资源
public static void close(ResultSet rs, PreparedStatement pstm, Connection conn) {
try {
if (rs != null) {
rs.close();
}
if (pstm != null) {
pstm.close();
}
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
第一代JDBCUtils测试:
package com.javaweb.utils;
import java.sql.*;
public class testJdbcUtils1 {
public static void main(String[] args) throws Exception {
Connection conn = JDBCUtils.getconnection();
String sql="update account set money = ? where id = ?";
PreparedStatement pstm = conn.prepareStatement(sql);
pstm.setString(1, "20000");
pstm.setString(2, "1");
int count=pstm.executeUpdate();
JDBCUtils.close( null,pstm, conn);
System.out.println(count);
}
}
2.编写第二代JDBCUtils并测试查看结果
在src下创建数据库连接配置文件：jdbc.properties
第二代JDBCUtils代码：
package com.javaweb.utils;
import java.io.FileReader;
import java.sql.*;
import java.util.Properties;
public class JDBCUtils2 {
private static String driver;
private static String url;
private static String user;
private static String password;
static {
try {
// 1. 创建Properties集合类。
Properties properties = new Properties();
// 2. 加载文件
properties.load(new FileReader(JDBCUtils.class.getClassLoader().getResource("jdbc.properties").getPath()));
driver = properties.getProperty("driver");
url = properties.getProperty("url");
user = properties.getProperty("user");
password = properties.getProperty("password");
// 注册驱动
Class.forName(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, user, password);
}
// 释放资源
public static void close(ResultSet rs, PreparedStatement pstm, Connection conn) {
try {
if (rs != null) {
rs.close();
}
if (pstm != null) {
pstm.close();
}
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
第二代JDBCUtils测试：
package com.javaweb.utils;
import java.sql.*;
public class testJdbcUtils2 {
public static void main(String[] args) throws Exception {
Connection conn = JDBCUtils2.getConnection();
String sql = "update account set money = ? where id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setDouble(1, 50000);
pstmt.setInt(2, 1);
int count = pstmt.executeUpdate();
System.out.println(count);
}
}
封装增删改查DAO
1.搭建数据库环境，创建库tb_user,插入测试记录
在MySQL中创建一个名称为db的数据库，然后在该数据库中创建一个tb_user表，再向表中插入3条数据。
create database db charset=utf8;
CREATE TABLE tb_user(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(40),
password VARCHAR(40),
email VARCHAR(60),
birthday DATE
)CHARACTER SET utf8 COLLATE utf8_general_ci;
INSERT INTO tb_user(username,password ,email,birthday) VALUES('zs','123456','[email protected]','1980-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('lisi','123456','[email protected]','1981-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('wangwu','123456','[email protected]','1979-12-04');
2.创建JavaBean：User.java
在src目录下，新建一个名称为chapter02.jdbc.example的包
创建JavaBean，User类的具体实现方式如下：
package com.javaweb.bean;
import java.util.Date;
public class user {
private int id;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
private String username;
private String password;
private String email;
private Date birthday;
}
创建数据库访问层DAO类封装增删改查代码：UserDao.java
package chapter02.jdbc.example;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import com.javaweb.bean.user;
public class UsersDao {
//添加用户的操作
public boolean insert(user user) {
Connection conn = null;
Statement stmt=null;
ResultSet rs = null;
try {
conn = JDBCUtils.getConnection();
stmt = conn.createStatement();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(user.getBirthday());
String sql = "INSERT INTO tb_user(id,username,password,email,birthday)"+
"VALUES("
+user.getId()
+",'"
+user.getUsername()
+"','"
+user.getPassword()
+"','"
+user.getEmail()
+"','"
+birthday + "')";
System.out.println(sql);
int num = stmt.executeUpdate(sql);
if (num > 0) {
return true;
}
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs,stmt,conn);
}
return false;
}
public ArrayList<user> findAll(){
Connection conn = null;
Statement stmt=null;
ResultSet rs = null;
ArrayList<user> list = new ArrayList<user>();
try {
conn = JDBCUtils.getConnection();
stmt = conn.createStatement();
String sql = "SELECT * FROM tb_user";
rs = stmt.executeQuery(sql);
while(rs.next()) {
user user = new user();
user.setId(rs.getInt("id"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setEmail(rs.getString("email"));
user.setBirthday(rs.getDate("birthday"));
list.add(user);
}
return list;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs, stmt, conn);
}
return null;
}
public user find(int id) {
Connection conn=null;
Statement stmt=null;
ResultSet rs = null;
try {
conn = JDBCUtils.getConnection();
stmt=conn.createStatement();
String sql = "SELECT * FROM tb_user WHERE id=" + id;
rs = stmt.executeQuery(sql);
while(rs.next()) {
user user = new user();
user.setId(rs.getInt("id"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setEmail(rs.getString("email"));
user.setBirthday(rs.getDate("birthday"));
return user;
}
return null;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs,stmt, conn);
}
return null;
}
public boolean delete(int id) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
conn = JDBCUtils.getConnection();
stmt= conn.createStatement();
String sql = "DELETE FROM tb_user WHERE id=" + id;
int num =stmt.executeUpdate(sql);
if(num > 0) {
return true;
}
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs, stmt,conn);
}
return false;
}
public boolean update(user user) {
Connection conn =null;
Statement stmt = null;
ResultSet rs = null;
try {
conn= JDBCUtils.getConnection();
stmt = conn.createStatement();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday =sdf.format(user.getBirthday());
String sql = "UPDATE tb_user set username='"+user.getUsername()
+"',password='"+user.getPassword() + "',email='"
+user.getEmail() + "',birthday='" + birthday
+"'WHERE id=" + user.getId();
int num = stmt.executeUpdate(sql);
if (num > 0) {
return true;
}
return false;
} catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtils.release(rs, stmt, conn);
}
return false;
}
}
4.利用JUnit对DAO的方法进行单元测试，并查看结果
创建测试类JDBCTESTl，利用JUnit对DAO-insert方法添加tb_user表中的数据:
在这里插入代码片`package chapter02.jdbc.example;
import java.util.Date;
import com.javaweb.bean.user;
@Test
public class JDBCTest {
public static void main(String[] args) {
//向users表插入一个用户信息
UsersDao ud = new UsersDao();
user user=new user();
user.setId(4);
user.setUsername("xiaoli");
user.setPassword("00000");
user.setEmail("[email protected]");
user.setBirthday(new Date());
boolean b= ud.insert(user);
System.out.println(b);
}
}`
测试结果：
创建测试类JDBCTEST03，利用JUnit对DAO-findAll方法根据ID查询tb_user表中数据：
package chapter02.jdbc.example;
import java.util.ArrayList;
import com.javaweb.bean.user;
public class FindAllUsersTest {
public static void main(String[] args) {
UsersDao usersDao = new UsersDao();
ArrayList<user> list = usersDao.findAll();
for (int i=0; i< list.size(); i++) {
System.out.println("第" + (i+1) + "条数据的username的值为："
+list.get(i).getUsername());
}
}
}
测试结果，成功查询出tb_user表中所有username值：
创建测试类JDBCTEST03，利用JUnit对DAO-find方法根据ID查询tb_user表中数据：
我们根据ID查询tb_user表中ID为13的数据库信息：
package chapter02.jdbc.example;
import static org.junit.Assert.*;
import org.junit.Test;
import com.javaweb.bean.user;
public class JDBCTEST03 {
@Test
public void testFind() throws Exception {
UsersDao dao= new UsersDao();
user user=dao.find(13);
System.out.println("id为13的User对象的name值为："+user.getUsername());
}
}
测试结果：
成功通过ID查询rb_user表中ID为13的username信息
创建测试类JDBCTEST04，利用JUnit对DAO-update方法方法根据ID更新tb_user表中数据：
package chapter02.jdbc.example;
import java.util.Date;
import org.junit.Test;
import com.javaweb.bean.user;
public class JDBCTEST04 {
@Test
public void testUpdate() throws Exception {
UsersDao dao= new UsersDao();
user user=new user();
user.setId(13);
user.setUsername("项秀才让");
user.setPassword("abc");
user.setEmail("[email protected]");
user.setBirthday(new Date());
boolean b=dao.update(user);
System.out.println(b);
}
}
测试结果：
成功修改ID为13的数据库记录信息！
创建测试类JdbcTest01，利用DAO-delete方法删除tb_user表中的数据
package chapter02.jdbc.example;
import org.junit.jupiter.api.Test;
class JdbcTest01 {
@Test
public void testDelete() {
UsersDao dao= new UsersDao();
boolean b=dao.delete(8);
System.out.println(b);
}
}
测试结果和sql查询结果：
用户登录程序
1.创建数据库表
在MySQL中使用一个名称为db_myweb的数据库，然后在该数据库中创建一个tb_user表，再向表中插入3条数据。
在这里插入代码片`Use db_myweb；
CREATE TABLE tb_user(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(40),
password VARCHAR(40),
email VARCHAR(60),
birthday DATE
)CHARACTER SET utf8 COLLATE utf8_general_ci;
插入数据：
INSERT INTO tb_user(username,password ,email,birthday) VALUES('zs','123456','zs@sina.com','1980-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('lisi','123456','lisi@sina.com','1981-12-04');
INSERT INTO tb_user(username,password ,email,birthday) VALUES('wangwu','123456','wangwu@sina.com','1979-12-04');
`
2.编写登录页面
在web目录下创建一个名称为login的JSP文件，在该文件中添加用于用户登录时输入用户信息的表单元素。
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/myweb/LoginServlet" method="post">
用户名：<input type="text" name="username"> <br>
密 码：<input type="password" name="password"> <br>
<input type="submit" value="登录">
</form>
</body>
</html>
3.编写工具类
由于每次操作数据库时，都需要加载数据库驱动、建立数据库连接以及关闭数据库连接，为了避免代码的重复书写，所以需要建立一个专门用于操作数据库的工具类。在src下创建一个包com.javaweb.utils，在包中创建一个封装了上述操作的工具类JDBCUtils。
package com.javaweb.utils;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.mysql.jdbc.Connection;
public class JDBCUtils {
// 加载驱动
static {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
// 获取连接
public static Connection getconnection() throws Exception {
String url = "jdbc:mysql://localhost:3306/db_myweb?useSSL=false";
String user = "root";
String password = "root";
Connection conn = (Connection) DriverManager.getConnection(url, user, password);
return conn;
}
// 释放资源
public static void close(ResultSet rs, java.sql.PreparedStatement pstm, java.sql.Connection conn) {
try {
if (rs != null) {
rs.close();
}
if (pstm != null) {
pstm.close();
}
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
4.UserDao增加方法按用户名和密码查询方法
// 根据username,password查找指定的user
public boolean findByUsernameAndPassword(String username,String password){
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
try {
// 获得数据的连接
conn = JDBCUtils.getConnection();
// 发送SQL语句
String sql = "select * from tb_user where username=? and password=?";
// 获得PreparedStatement对象
pstmt = (PreparedStatement) conn.prepareStatement(sql);
pstmt.setString(1, username);
pstmt.setString(2, password);
rs = pstmt.executeQuery();
// 处理结果集
if (rs.next())
return true;
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, pstmt, conn);
}
return false;
}
5.实现登录功能的LoginServlet
package com.javaweb.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
String username=request.getParameter("username");
String password=request.getParameter("password");
if(username!=null&&password!=null&&!username.equals("")&&!password.equals("")) {
UserDao dao=new UserDao();
boolean b=dao.findByUsernameAndPassword(username, password);
if(b)
out.print("欢迎登录！");
else
out.print("用户名或密码不正确！");
}else
out.print("用户名或密码不能为空！");
}
}
运行项目，查看效果
C3P0数据库连接池实验
1.导入JAR包c3p0-0.9.2.1.jar和mchange-commons-java-0.2.3.4.jar
在项目中导入JAR包c3p0-0.9.2.1.jar和mchange-commons-java-0.2.3.4.jar，并使用C3P0数据库连接池对象获取Connection对象。
2.创建C3P0Test测试用例类，测试代码
package com.javaweb.test;
import java.sql.Connection;
import java.sql.SQLException;
import org.junit.Test;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class C3P0Test {
@Test
public void test() throws PropertyVetoException, SQLException, java.beans.PropertyVetoException {
ComboPooledDataSource ds = new ComboPooledDataSource();
ds.setDriverClass("com.mysql.jdbc.Driver");
ds.setJdbcUrl("jdbc:mysql://localhost:3306/db_myweb?useSSL=false");
ds.setUser("root");
ds.setPassword("root");
ds.setInitialPoolSize(5);
ds.setMaxPoolSize(10);
Connection conn = ds.getConnection();
System.out.println(conn);
}
}
测试结果：
3.在项目的src根目录下创建一个c3p0-config.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl"> jdbc:mysql://localhost:3306/db_myweb?useSSL=false</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="checkoutTimeout">30000</property>
<property name="initialPoolSize">10</property>
<property name="maxIdleTime">30</property>
<property name="maxPoolSize">10</property>
<property name="minPoolSize">2</property>
<property name="maxStatements">200</property>
</default-config>
</c3p0-config>
4.创建C3P0Test测试用例类，测试代码
package chapter02.jdbc.example;
import java.beans.PropertyVetoException;
import java.sql.SQLException;
import org.junit.Test;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import com.mysql.jdbc.Connection;
public class C3P0Test {
@Test
public void testC3P0() throws SQLException {
ComboPooledDataSource ds= new ComboPooledDataSource();
System.out.println(ds.getConnection());
}
}
测试结果：
测试成功！
5.封装DataSourceUtils工具类
package com.javaweb.test;
import java.sql.SQLException;
import com.mysql.jdbc.Connection;
public class DataSourceUtils {
private static ComboPooledDataSource ds=new ComboPooledDataSource();
public static ComboPooledDataSource getDataSource()
{
return ds;
}
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
}
6.修改UserDao从DataSourceUtils工具类，获取数据库连接，并测试结果。
BUtils工具增删改查
1.将commons-dbutils-1.7.jar添加到项目的lib目录中
2.创建UserDaoQr.java，编写QueryRunner示例代码：增加、删除、修改
package cn.itcast.jdbc.dao;
import java.sql.SQLException;
import java.util.List;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import cn.itcast.jdbc.javabean.User;
import cn.itcast.jdbc.utils.DataSourceUtils;
public class UserDaoQr {
public boolean insert(User user) throws SQLException {
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "INSERT INTO t_user(id,username,password) VALUES(null,?,?)";
int num= r.update(sql,user.getName(),user.getPassword());
if (num > 0) {
return true;
}
return false;
}
public boolean update(User user) throws SQLException {
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "update t_user set username=?,password=?";
int num= r.update(sql,user.getName(),user.getPassword());
if (num > 0) {
return true;
}
return false;
}
public boolean delete(int id) throws SQLException {
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "delete from t_user where id=?";
int num= r.update(sql,id);
if (num > 0) {
return true;
}
return false;
}
public User find(int id) throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user WHERE id=?";
User user= r.query(sql, new BeanHandler<User>(User.class),id);
return user;
}
public List<User> findAll() throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user";
List<User> list=r.query(sql, new BeanListHandler<User>(User.class));
return list;
}
}
3.QueryRunner示例代码：单元测试增删改代码
单元测试增加数据：
package cn.itcast.jdbc.dao;
import java.sql.SQLException;
import org.junit.Test;
import cn.itcast.jdbc.javabean.User;
public class test {
@Test
public void testInsert() throws SQLException {
UserDaoQr dao=new UserDaoQr();
User user=new User();
user.setName("svdviming");
user.setPassword("dad2dadadadad3");
boolean b=dao.insert(user);
if(b)
System.out.println("数据插入成功！");
else
System.out.println("数据插入失败！");
}
}
单元测试删除数据：
@Test
public void testDelete() throws SQLException {
UserDaoQr dao=new UserDaoQr();
boolean b=dao.delete(3);
if(b)
System.out.println("数据删除成功！");
else
System.out.println("数据删除失败！");
}
}
测试结果：
数据删除成功！
4.QueryRunner示例代码：查询单个，并测试
package cn.itcast.jdbc.dao;
import java.sql.SQLException;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import cn.itcast.jdbc.javabean.User;
import cn.itcast.jdbc.utils.DataSourceUtils;
public class UserDaoQr {
public User find(int id) throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user WHERE id=?";
User user= r.query(sql, new BeanHandler<User>(User.class),id);
return user;
}
}
测试ID为2的数据：
package cn.itcast.jdbc.dao;
import java.sql.SQLException;
import org.junit.Test;
import cn.itcast.jdbc.javabean.User;
public class test {
@Test
public void testFind() throws SQLException {
UserDaoQr dao=new UserDaoQr();
User user=dao.find(2);
System.out.println("name="+user.getName());
}
}
测试结果：
成功查询ID=2的数据！
5.QueryRunner示例代码：查询全部，并测试
package cn.itcast.jdbc.dao;
import java.sql.SQLException;
import java.util.List;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import cn.itcast.jdbc.javabean.User;
import cn.itcast.jdbc.utils.DataSourceUtils;
public class UserDaoQr {
public List<User> findAll() throws SQLException{
QueryRunner r = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "SELECT * FROM user";
List<User> list=r.query(sql, new BeanListHandler<User>(User.class));
return list;
}
}
测试结果：
成功通过 findAll测试查询表中数据信息。