详细说明关于Java的数据库连接(JDBC) 详细说明关于Java的数据库连接

Java的数据库连接(JDBC)

1、什么是JDBC
2、JDBC的原理
3、演示JDBC的使用
4、数据库连接方式
5、JDBC的查询
6、SQL注入
7、预处理查询

7.1 查询已解决注入问题
7.2 插入,更新,删除

8、工具类开发

9、JDBC事务

10、批处理

11、数据库连接池

11.1 数据库连接池基本介绍
11.2 JDBC的数据库连接池使用
11.3 数据库连接池的种类
11.4 C3P0连接池
11.5 Druid连接池

12、Apache-DBUtils

12.1 ArrayList模拟
12.2 Apache-DBUtils

13、BasicDao

13.1 BasicDAO类
13.2 domain中的类
13.3 测试类

Java的数据库连接(JDBC)
1、什么是JDBC
JDBC（JavaDataBase Connectivity）就是Java数据库连接，说白了就是用Java语言来操作数据库。原来我们操作数据库是在控制台使用SQL语句来操作数据库，JDBC是用Java语言向数据库发送SQL语句。

2、JDBC的原理
早期SUN公司的天才们想编写一套可以连接天下所有数据库的API，但是当他们刚刚开始时就发现这是不可完成的任务，因为各个厂商的数据库服务器差异太大了。后来SUN开始与数据库厂商们讨论，最终得出的结论是，由SUN提供一套访问数据库的规范（就是一组接口），并提供连接数据库的协议标准，然后各个数据库厂商会遵循SUN的规范提供一套访问自己公司的数据库服务器的API出现。SUN提供的规范命名为JDBC，而各个厂商提供的，遵循了JDBC规范的，可以访问自己数据库的API被称之为驱动！JDBC是接口，而JDBC驱动才是接口的实现，没有驱动无法完成数据库连接！每个数据库厂商都有自己的驱动，用来连接自己公司的数据库。

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3、演示JDBC的使用
通过下载MySQL的驱动jar文件，将其添加到项目中间，在注册驱动时要指定为已经下载好的驱动。

package jdbc; import com.mysql.jdbc.Driver; //这是我们驱动的路径import java.sql.Connection; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties; public class Jdbc01 {public static void main(String[] args) throws SQLException {//1.注册驱动Driver driver = new Driver(); //2.得到连接//jdbc:mysql:// 规定好的协议localhost 连接的地址3306 监听的端口 test_table 连接的数据库String url = "jdbc:mysql://localhost:3306/test_table"; Properties properties = new Properties(); //user和password 规定好的不能随意改properties.setProperty("user", "root"); //properties.setProperty("password", "161142"); Connection connect = driver.connect(url, properties); //相当于网络连接//3.执行sql语句//String sql = "insert into actor values(null,'syj','女','2000-05-26','110')"; String sql = "update actor set name = 'xhj' where id =2"; Statement statement = connect.createStatement(); int rows = statement.executeUpdate(sql); //返回影响的行数if (rows > 0) System.out.println("添加成功"); else System.out.println("添加失败"); //4.关闭连接资源statement.close(); connect.close(); }}

4、数据库连接方式

public class JdbcConn {@Test/* 第一种 */public void testConn01() throws SQLException {//获取Driver实现类对象Driver driver = new Driver(); String url = "jdbc:mysql://localhost:3306/test_table"; Properties properties = new Properties(); properties.setProperty("user", "root"); properties.setProperty("password", "161142"); Connection connect = driver.connect(url, properties); System.out.println(connect); }@Test/* 第二种 */public void testConn02() throws Exception{//使用反射加载Driver类,动态加载,可以通过配置文件灵活使用各种数据库Class aClass = Class.forName("com.mysql.jdbc.Driver"); Driver driver = (Driver) aClass.getDeclaredConstructor().newInstance(); String url = "jdbc:mysql://localhost:3306/test_table"; Properties properties = new Properties(); properties.setProperty("user", "root"); properties.setProperty("password", "161142"); Connection connect = driver.connect(url, properties); System.out.println(connect); }@Test/* 第三种 *///DriverManager统一来管理Driverpublic void testConn03() throws Exception{//使用反射加载Driver类Class aClass = Class.forName("com.mysql.jdbc.Driver"); Driver driver = (Driver) aClass.getDeclaredConstructor().newInstance(); //创建url和user和passwordString url = "jdbc:mysql://localhost:3306/test_table"; String user = "root"; String password = "161142"; DriverManager.registerDriver(driver); //注册Driver驱动Connection connection = DriverManager.getConnection(url, user, password); System.out.println(connection); }@Test/* 第四种 */public void testConn04() throws Exception{//使用反射加载Driver类Class.forName("com.mysql.jdbc.Driver"); /* Class.forName("com.mysql.jdbc.Driver")在底层加载Driver时自动完成注册驱动,简化代码//在底层加载Driver时会自动加载静态代码块static {try {DriverManager.registerDriver(new Driver()); } catch (SQLException var1) {throw new RuntimeException("Can't register driver!"); }}*///Class.forName("com.mysql.jdbc.Driver"); /*Class.forName("com.mysql.jdbc.Driver"); 这句话也可以去掉mysql驱动5.1.6可以无需CLass.forName(“com.mysql.jdbc.Driver"); 从jdk1.5以后使用了jdbc4,不再需要显示调用class.forName()注册驱动而是自动调用驱动jar包下META-INF\services\java.sqI.Driver文本中的类名称去注册建议还是写上,更加明确*///创建url和user和passwordString url = "jdbc:mysql://localhost:3306/test_table"; String user = "root"; String password = "161142"; Connection connection = DriverManager.getConnection(url, user, password); System.out.println(connection); }@Test/* 第五种(推荐使用) */public void testConn05() throws Exception{//在方式4的情况下,将信息放到配置文件里,利于后续可持续操作//获取配置文件信息Properties properties = new Properties(); properties.load(new FileInputStream("src\\mysql.properties")); //获取相关信息String user = properties.getProperty("user"); String password = properties.getProperty("password"); String url = properties.getProperty("url"); String driver = properties.getProperty("driver"); Class.forName(driver); //加载Driver类,建议加上Connection connection = DriverManager.getConnection(url, user, password); System.out.println(connection); }}

5、JDBC的查询
使用ResultSet 记录查询结果
ResultSet：底层使用ArrayList 存放每一行数据(二维字节数组,每一维表示一行中的一个数据)
Resultment：用于执行静态SQL语句并返回其生成的结果的对象，是一个接口，需要各个数据库厂家来实现。(实际中我们一般不用这个)

public class jdbc03 {public static void main(String[] args) throws Exception {Properties properties = new Properties(); properties.load(new FileInputStream("src\\mysql.properties")); String user = properties.getProperty("user"); String password = properties.getProperty("password"); String url = properties.getProperty("url"); String driver = properties.getProperty("driver"); Class.forName(driver); Connection connection = DriverManager.getConnection(url, user, password); Statement statement = connection.createStatement(); ResultSet resultSet = statement.executeQuery("select id,`name`,sex,borndate from actor; "); while (resultSet.next()){ //resultSet.previous(); //向上移动一行int id = resultSet.getInt(1); //int id = resultSet.getInt("id"); //也可以按照列明来获取String name = resultSet.getString(2); String sex = resultSet.getString(3); Date date = resultSet.getDate(4); //Object object = resultSet.getObject(索引|列明); //对象形式操作(分情况考虑)System.out.println(id + "\t" + name + "\t" + sex + "\t" + date); }statement.close(); connection.close(); }}

6、SQL注入
SQL注入：是利用某些系统没有对用户输入的数据进行充分的检查,而在用户输入数据中注入非法的SQL语句段或命令,恶意攻击数据库。
例如下列代码实现了注入问题(而Statement就存在这个问题，所以实际开发过程中不用它)

create table admit(name varchar(32),password varchar(32)); insert into admit values('tom','1234'); select * from admit where name = 'tom' and password = '1234'; # 输出 tom 1234# 如果有人输入 name 为 1' orpassword 为or '1' = '1# 那么select 就变成select * from admit where name = '1' or ' and password = ' or '1' = '1'; # 其中'1' = '1'永远成立

7、预处理查询
使用PreparedStatement代替Statement就避免了注入问题，通过传入**?** 代替拼接 (PreparedStatement接口继承了Statement接口)
PreparedStatement的好处

不再使用+拼接sql语句，减少语法错误
有效的解决了sql注入问题!
大大减少了编译次数，效率较高

7.1 查询已解决注入问题

public class jdbc04 {public static void main(String[] args) throws Exception {Scanner scanner = new Scanner(System.in); System.out.print("请输入用户名:"); String name = scanner.nextLine(); System.out.print("请输入密码:"); String pwd = scanner.nextLine(); Properties properties = new Properties(); properties.load(new FileInputStream("src\\mysql.properties")); String user = properties.getProperty("user"); String password = properties.getProperty("password"); String url = properties.getProperty("url"); String driver = properties.getProperty("driver"); Class.forName(driver); Connection connection = DriverManager.getConnection(url, user, password); //Statement statement = connection.createStatement(); //preparedStatement是PreparedStatement实现类的对象PreparedStatement preparedStatement = connection.prepareStatement("select `name` ,`password` " +"from admit where name = ? and password = ?"); preparedStatement.setString(1,name); //?号下标从1开始preparedStatement.setString(2,pwd); ResultSet resultSet = preparedStatement.executeQuery(); if (resultSet.next()) System.out.println("登录成功"); else System.out.println("登陆失败"); preparedStatement.close(); connection.close(); }}

7.2 插入,更新,删除

public class jdbc05 {public static void main(String[] args) throws Exception {Scanner scanner = new Scanner(System.in); System.out.print("请输入用户名:"); String name = scanner.nextLine(); System.out.print("请输入密码:"); String pwd = scanner.nextLine(); Properties properties = new Properties(); properties.load(new FileInputStream("src\\mysql.properties")); String user = properties.getProperty("user"); String password = properties.getProperty("password"); String url = properties.getProperty("url"); String driver = properties.getProperty("driver"); Class.forName(driver); Connection connection = DriverManager.getConnection(url, user, password); //添加String sql1 = "insert into admit values(?,?)"; //修改String sql2 = "update admit set name = ? where name = ? and password = ?"; //删除String sql3 = "delete from admit where name = ? and password = ?"; PreparedStatement preparedStatement = connection.prepareStatement(sql3); //preparedStatement.setString(1,name+"plas"); //?号下标从1开始//preparedStatement.setString(2,name); //preparedStatement.setString(3,pwd); preparedStatement.setString(1,name); preparedStatement.setString(2,pwd); int rows = preparedStatement.executeUpdate(); if (rows > 0) System.out.println("操作成功"); else System.out.println("操作失败"); preparedStatement.close(); connection.close(); }}

8、工具类开发
由于在进行数据库操作时，有些步骤是重复的，如连接，关闭资源等操作。
工具类

package utils; import java.sql.*; import java.io.FileInputStream; import java.util.Properties; public class JDBCUtils {private static String user; //用户名private static String password; //密码private static String url; //连接数据库的urlprivate static String driver; //驱动//静态代码块进行行初始化static {try {Properties properties = new Properties(); properties.load(new FileInputStream("src\\mysql.properties")); user = properties.getProperty("user"); password = properties.getProperty("password"); url = properties.getProperty("url"); driver = properties.getProperty("driver"); } catch (Exception e) {//实际开发过程中(将编译异常,改成运行异常,用户可以捕获异常,也可以默认处理该异常)throw new RuntimeException(e); }}//连接public static Connection getConnection(){try {return DriverManager.getConnection(url,user,password); } catch (SQLException e) {throw new RuntimeException(e); }}//关闭资源public static void close(ResultSet set, Statement statement,Connection connection){try {if (set != null) set.close(); if (statement != null)statement.close(); if (connection != null)connection.close(); } catch (SQLException e) {throw new RuntimeException(e); }}}

【详细说明关于Java的数据库连接(JDBC)】应用:

public class JdbcUtilsTest {@Test//测试select操作public void testSelect() {Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; try {//得到连接connection = JDBCUtils.getConnection(); //设置sqlString sql = "select * from actor where id = ?"; //创建PreparedStatementpreparedStatement = connection.prepareStatement(sql); //占位赋值preparedStatement.setInt(1,2); //执行resultSet = preparedStatement.executeQuery(); while (resultSet.next()) {/* 也可以这样写int id = resultSet.getInt("id"); String name = resultSet.getString("name"); String sex = resultSet.getString("sex"); Date date = resultSet.getDate("borndate"); String phone = resultSet.getString("phone"); */int id = resultSet.getInt(1); String name = resultSet.getString(2); String sex = resultSet.getString(3); Date date = resultSet.getDate(4); String phone = resultSet.getString(5); System.out.println(id + "\t" + name + "\t" + sex + "\t" + date + "\t" + phone); }} catch (SQLException e) {e.printStackTrace(); } finally {JDBCUtils.close(resultSet, preparedStatement, connection); }}@Test//测试DML操作public void testDML() {Connection connection = null; PreparedStatement preparedStatement = null; try {//得到连接connection = JDBCUtils.getConnection(); //设置sqlString sql = "update actor set name = ?,sex = ? where id = ?"; //创建PreparedStatementpreparedStatement = connection.prepareStatement(sql); //占位符赋值preparedStatement.setString(1, "sxy"); preparedStatement.setString(2, "男"); preparedStatement.setInt(3, 2); //执行preparedStatement.executeUpdate(); } catch (SQLException e) {e.printStackTrace(); } finally {JDBCUtils.close(null, preparedStatement, connection); }}}

9、JDBC事务

public class Jdbc06 {public static void main(String[] args) {Connection connection = null; PreparedStatement preparedStatement = null; try {connection = JDBCUtils.getConnection(); connection.setAutoCommit(false); //关闭自动提交(开启事务)//第一个动作String sql = "update actor set phone = phone - 10 where id = 2"; preparedStatement = connection.prepareStatement(sql); preparedStatement.executeUpdate(); //int i = 1/0; 异常//第二个动作sql = "update actor set phone = phone + 10 where id = 1"; preparedStatement = connection.prepareStatement(sql); preparedStatement.executeUpdate(); //提交事务connection.commit(); } catch (Exception e) {System.out.println("有异常存在,撤销sql服务"); try {connection.rollback(); //回滚到事务开始的地方} catch (SQLException throwables) {throwables.printStackTrace(); }e.printStackTrace(); } finally {JDBCUtils.close(null, preparedStatement, connection); }}}

10、批处理

public class Jdbc07 {@Test//普通处理5000条插入数据执行时间169839public void test01() {Connection connection = null; PreparedStatement preparedStatement = null; try {connection = JDBCUtils.getConnection(); String sql = "insert into actor(id,`name`,sex) values (?,?,'男')"; preparedStatement = connection.prepareStatement(sql); long begin = System.currentTimeMillis(); for (int i = 0; i < 5000; i++) {preparedStatement.setString(1, 3 + i + ""); preparedStatement.setString(2, "sxy" + (i + 1)); preparedStatement.executeUpdate(); }long end = System.currentTimeMillis(); System.out.println(end - begin); } catch (Exception e) {e.printStackTrace(); } finally {JDBCUtils.close(null, preparedStatement, connection); }}@Test//批处理执行时间429public void test02() {Connection connection = null; PreparedStatement preparedStatement = null; try {connection = JDBCUtils.getConnection(); String sql = "insert into actor(id,`name`,sex) values (?,?,'男')"; preparedStatement = connection.prepareStatement(sql); long begin = System.currentTimeMillis(); for (int i = 0; i < 5000; i++) {preparedStatement.setString(1, 3 + i + ""); preparedStatement.setString(2, "sxy" + (i + 1)); //将sql语句加入批处理包中preparedStatement.addBatch(); /*preparedStatement.addBatch()在底层把每一条数据加入到ArrayList执行过程:检查本条sql中的语法问题 -> 把本条sql语句加入到ArrayList -> 每1000条执行一次批处理优点:减少了编译次数,又减少了运行次数,效率大大提高还需要在properties配置文件中将url加上?rewriteBatchedStatements=trueurl=jdbc:mysql://localhost:3306/test_table?rewriteBatchedStatements=true*///当有1000条时,在进行处理if ((i + 1) % 1000 == 0) {preparedStatement.executeBatch(); //清空批处理包preparedStatement.clearBatch(); }}long end = System.currentTimeMillis(); System.out.println(end - begin); } catch (Exception e) {e.printStackTrace(); } finally {JDBCUtils.close(null, preparedStatement, connection); }}}

11、数据库连接池
由于有很多用户连接数据库，而数据库连接数量又是有限制的，而且就算连接并且关闭也是很耗时，所以就有了引入了数据库连接池可以很好的来解决这个问题。下面是普通连接数据库连接并且关闭5000次所耗时间6249毫秒，可以发下时间相对很长。

public class ConQuestion {public static void main(String[] args) {//看看连接-关闭 connection 会耗用多久long start = System.currentTimeMillis(); System.out.println("开始连接....."); for (int i = 0; i < 5000; i++) {//使用传统的jdbc方式，得到连接Connection connection = JDBCUtils.getConnection(); //做一些工作，比如得到PreparedStatement ，发送sql//..........//关闭JDBCUtils.close(null, null, connection); }long end = System.currentTimeMillis(); System.out.println("传统方式5000次耗时=" + (end - start)); //传统方式5000次耗时=6249}}

11.1 数据库连接池基本介绍

预先在缓冲池中放入一定数量的连接,当需要建立数据库连接时，只需从“缓冲池”中取出一个，使用完毕之后再放回去。
数据库连接池负责分配，管理和释放数据库连接，它允许应用程序重复使用一个现有的数据库连接，而不是重新建立一个。
当应用程序向连接池请求的连接数超过最大连接数量时，这些请求将被加入到等待队列中。

11.2 JDBC的数据库连接池使用 JDBC的数据库连接池使用javax.sql.DataSource来表示，DataSource只是一个接口，该接口通常由第三方提供实现。

11.3 数据库连接池的种类

C3P0 数据库连接池，速度相对较慢，稳定性不错(hibernate，spring)。(用的较多)
DBCP数据库连接池，速度相对c3p0较快，但不稳定。
Proxool数据库连接池，有监控连接池状态的功能，稳定性较c3p0差一点。
BoneCP 数据库连接池，速度快。
Druid (德鲁伊)是阿里提供的数据库连接池，集DBCP，C3P0，Proxool优点于身的数据库连接池。(应用最广)

11.4 C3P0连接池利用C3P0连接池再次尝试连接5000次数据库可以发现耗时方式一仅仅花了456毫秒，第二种通过配置文件操作也是花了419毫秒差不多的时间，值得说的是这个连接池连接配置文件不能是我们自己写，官方有给定的模板(c3p0.config.xml)。

public class C3P0_ {@Test//方式一: 相关参数,在程序中指定user,url,password等public void testC3P0_1() throws Exception {//创建一个数据源对象ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource(); //通过配合文件获取相关连接信息Properties properties = new Properties(); properties.load(new FileInputStream("src\\mysql.properties")); String user = properties.getProperty("user"); String password = properties.getProperty("password"); String url = properties.getProperty("url"); String driver = properties.getProperty("driver"); //给数据源(comboPooledDataSource)设置相关参数//连接管理是由comboPooledDataSource(连接池)来管理的comboPooledDataSource.setDriverClass(driver); //设置驱动comboPooledDataSource.setJdbcUrl(url); comboPooledDataSource.setUser(user); comboPooledDataSource.setPassword(password); //初始化数据源的连接数comboPooledDataSource.setInitialPoolSize(10); //数据库连接池最大容量,如果还有连接请求,那么就会将该请求放入等待队列中comboPooledDataSource.setMaxPoolSize(50); //测试连接池的效率, 测试对mysql 5000次操作long start = System.currentTimeMillis(); for (int i = 0; i < 5000; i++) {//getConnection()这个方法就是重写了DataSource接口的方法Connection connection = comboPooledDataSource.getConnection(); connection.close(); }long end = System.currentTimeMillis(); //c3p0 5000连接mysql 耗时=456System.out.println("c3p0 5000连接mysql 耗时=" + (end - start)); comboPooledDataSource.close(); }//第二种方式使用配置文件模板来完成//将C3P0 提供的 c3p0.config.xml 拷贝到 src目录下//该文件指定了连接数据库和连接池的相关参数@Testpublic void testC3P0_02() throws SQLException {ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource("sxy"); //测试5000次连接mysqllong start = System.currentTimeMillis(); for (int i = 0; i < 5000; i++) {Connection connection = comboPooledDataSource.getConnection(); connection.close(); }long end = System.currentTimeMillis(); //c3p0的第二种方式(5000) 耗时=419System.out.println("c3p0的第二种方式(5000) 耗时=" + (end - start)); }}

11.5 Druid连接池在使用Druid连接池连接数据库500000次耗时643毫秒,而C3P0500000次连接耗时2373毫秒,很显然Druid连接速度更快。

public class Druid_ {@Testpublic void testDruid() throws Exception {//1.加入Druid jar包//2.加入配置文件 druid.properties 放到src目录下//3.创建Properties对象Properties properties = new Properties(); properties.load(new FileInputStream("src\\druid.properties")); //4.创建一个指定参数的数据库连接池DataSource dataSource = DruidDataSourceFactory.createDataSource(properties); long start = System.currentTimeMillis(); for (int i = 0; i < 500000; i++) {Connection connection = dataSource.getConnection(); connection.close(); }long end = System.currentTimeMillis(); //Druid的500000次创建耗时=643System.out.println("Druid的500000次创建耗时=" + (end - start)); }}

对应的工具类

public class JDBCUtilsByDruid {private static DataSource ds; //在静态代码块完成 ds初始化static {Properties properties = new Properties(); try {properties.load(new FileInputStream("src\\druid.properties")); ds = DruidDataSourceFactory.createDataSource(properties); } catch (Exception e) {e.printStackTrace(); }}//编写getConnection方法public static Connection getConnection() throws SQLException {return ds.getConnection(); }//关闭连接:在数据库连接池技术中,close不是真的断掉连接,而是把使用的Connection对象放回连接池public static void close(ResultSet resultSet, Statement statement, Connection connection) {try {if (resultSet != null) resultSet.close(); if (statement != null) statement.close(); if (connection != null) connection.close(); } catch (SQLException e) {throw new RuntimeException(e); }}}

使用工具类：

public class TestUtilsByDruid {@Testpublic void testSelect() {Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; try {//得到连接connection = JDBCUtilsByDruid.getConnection(); System.out.println(connection.getClass()); //connection 的运行类型 class com.alibaba.druid.pool.DruidPooledConnection//设置sqlString sql = "select * from actor where id = ?"; //创建PreparedStatementpreparedStatement = connection.prepareStatement(sql); //占位赋值preparedStatement.setInt(1, 2); //执行resultSet = preparedStatement.executeQuery(); while (resultSet.next()) {int id = resultSet.getInt(1); String name = resultSet.getString(2); String sex = resultSet.getString(3); Date date = resultSet.getDate(4); String phone = resultSet.getString(5); System.out.println(id + "\t" + name + "\t" + sex + "\t" + date + "\t" + phone); }} catch (SQLException e) {e.printStackTrace(); } finally {JDBCUtilsByDruid.close(resultSet, preparedStatement, connection); }}}

12、Apache-DBUtils

由于resultSet存放数据集合，在connection关闭时，resultSet结果集无法使用。所以为了使用这些数据，也有JDBC官方提供的文件Apache-DBUtils来存放数据。

12.1 ArrayList模拟
ArrayList模拟Apache-DBUtils
Actor类用来保存Actor表中的数据用的。

public class Actor { //Javabean, POJO, Domain对象private Integer id; private String name; private String sex; private Date borndate; private String phone; public Actor() { //一定要给一个无参构造器[反射需要]}public Actor(Integer id, String name, String sex, Date borndate, String phone) {this.id = id; this.name = name; this.sex = sex; this.borndate = borndate; this.phone = phone; }public Integer getId() { return id; }public void setId(Integer id) { this.id = id; }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 Date getBorndate() { return borndate; }public void setBorndate(Date borndate) { this.borndate = borndate; }public String getPhone() { return phone; }public void setPhone(String phone) { this.phone = phone; }@Overridepublic String toString() {return "\nActor{" + "id=" + id + ", name='" + name + '\'' +", sex='" + sex + '\'' + ", borndate=" + borndate +", phone='" + phone + '\'' + '}'; }}

用ArrayList来存放数据

public class LikeApDB {@Testpublic /*也可以返回ArrayList*/void testSelectToArrayList() {Connection connection = null; String sql = "select * from actor where id >= ?"; PreparedStatement preparedStatement = null; ResultSet resultSet = null; ArrayList list = new ArrayList<>(); try {connection = JDBCUtilsByDruid.getConnection(); System.out.println(connection.getClass()); preparedStatement = connection.prepareStatement(sql); preparedStatement.setInt(1, 1); resultSet = preparedStatement.executeQuery(); while (resultSet.next()) {int id = resultSet.getInt("id"); String name = resultSet.getString("name"); //getName()String sex = resultSet.getString("sex"); //getSex()Date borndate = resultSet.getDate("borndate"); String phone = resultSet.getString("phone"); //把得到的 resultSet 的记录，封装到 Actor对象，放入到list集合list.add(new Actor(id, name, sex, borndate, phone)); }System.out.println("list集合数据=" + list); for(Actor actor : list) {System.out.println("id=" + actor.getId() + "\t" + actor.getName()); }} catch (SQLException e) {e.printStackTrace(); } finally {//关闭资源JDBCUtilsByDruid.close(resultSet, preparedStatement, connection); }//因为ArrayList 和 connection 没有任何关联，所以该集合可以复用.//returnlist; }}

12.2 Apache-DBUtils 基本介绍
commons-dbutils是 Apache组织提供的一个开源JDBC工具类库，它是对JDBC的封装，使用dbutils能极大简化jdbc编码的工作量。
DbUtils类

QueryRunner类：该类封装了SQL的执行，是线程安全的。可以实现增，删，改，查，批处理
使用QueryRunner类实现查询。
ResultSetHandler接口：该接口用于处理 java.sql.ResultSet，将数据按要求转换为另一种形式

应用实例

使用Apache-DBUtils工具+数据库连接池(Druid)方式，完成对一个表的增删改查。

package datasourse; import ApDB.Actor; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.BeanHandler; import org.apache.commons.dbutils.handlers.BeanListHandler; import org.apache.commons.dbutils.handlers.ScalarHandler; import org.junit.jupiter.api.Test; import java.sql.Connection; import java.sql.SQLException; import java.util.List; public class DBUtils_Use {@Test//查询多条数据public void testQueryMany() throws Exception {//1.得到连接(Druid)Connection connection = JDBCUtilsByDruid.getConnection(); //2.使用 DBUtils 类和接口,先引入 DBUtils jar文件 ,放到src目录下//3.创建QueryRunnerQueryRunner queryRunner = new QueryRunner(); //4.执行相应的方法,返回ArrayList结果集String sql = "select * from actor where id >= ?"; //String sql = "select id,`name` from actor where id >= ?"; /*(1) query 方法就是执行sql 语句，得到resultSet ---封装到 --> ArrayList 集合中(2) 返回集合(3) connection: 连接(4) sql : 执行的sql语句(5) new BeanListHandler<>(Actor.class): 在将resultSet -> Actor 对象 -> 封装到 ArrayList底层使用反射机制去获取Actor 类的属性，然后进行封装(6) 1 就是给 sql 语句中的? 赋值，可以有多个值，因为是可变参数Object... params(7) 底层得到的resultSet ,会在query 关闭, 关闭PreparedStatement*/List query =queryRunner.query(connection, sql, new BeanListHandler<>(Actor.class), 1); /*** 分析 queryRunner.query方法源码分析* public T query(Connection conn, String sql, ResultSetHandler rsh, Object... params) throws SQLException {*PreparedStatement stmt = null; //定义PreparedStatement*ResultSet rs = null; //接收返回的 ResultSet*Object result = null; //返回ArrayList**try {*stmt = this.prepareStatement(conn, sql); //创建PreparedStatement*this.fillStatement(stmt, params); //对sql 进行 ? 赋值*rs = this.wrap(stmt.executeQuery()); //执行sql,返回resultset*result = rsh.handle(rs); //返回的resultset --> arrayList[result] [使用到反射，对传入class对象处理]*} catch (SQLException var33) {*this.rethrow(var33, sql, params); *} finally {*try {*this.close(rs); //关闭resultset*} finally {*this.close((Statement)stmt); //关闭preparedstatement对象*}*}**return result; *}*/for (Actor actor : query) {System.out.print(actor); }JDBCUtilsByDruid.close(null,null,connection); }@Test//查询单条记录public void testQuerySingle() throws SQLException {Connection connection = JDBCUtilsByDruid.getConnection(); QueryRunner queryRunner = new QueryRunner(); String sql = "select * from actor where id = ?"; //已知查询的是单行,所以就用BeanHandler,返回一个对应的对象Actor query = queryRunner.query(connection, sql, new BeanHandler<>(Actor.class), 2); System.out.print(query); JDBCUtilsByDruid.close(null,null,connection); }@Test//查询单行单列(某个信息)返回一个Object对象public void testQuerySingleObject() throws SQLException {Connection connection = JDBCUtilsByDruid.getConnection(); QueryRunner queryRunner = new QueryRunner(); String sql = "select `name` from actor where id = ?"; //已知查询的是单行单列,所以就用BeanHandler,返回一个ObjectObject query = queryRunner.query(connection, sql, new ScalarHandler(), 1); System.out.println(query); JDBCUtilsByDruid.close(null,null,connection); }@Test//演示DML操作(insert,update,delete)public void testDML() throws SQLException {Connection connection = JDBCUtilsByDruid.getConnection(); QueryRunner queryRunner = new QueryRunner(); //String sql = "update actor set phone = ? where id = ?"; //int affectedRow = queryRunner.update(connection, sql, "110", 2); String sql = "insert into actor values(?,?,?,?,?)"; int affectedRow = queryRunner.update(connection, sql, 3, "xhj", "女", "2000-05-26", "110"); //String sql = "delete from actor where id = ?"; //int affectedRow = queryRunner.update(connection, sql, 5004); System.out.println(affectedRow > 0 ? "OK" : "NO"); JDBCUtilsByDruid.close(null,null,connection); }}

13、BasicDao
引入问题

SQL语句是固定，不能通过参数传入，通用性不好，需要进行改进，更方便执行增删改查
对于select 操作，如果有返回值，返回类型不能固定，需要使用泛型
将来的表很多，业务需求复杂，不可能只靠一个JAVA类完成。

所以在实际开发中，也有解决办法 —BasicDao

13.1 BasicDAO类

public class BasicDAO {//泛型指定具体的类型private QueryRunner queryRunner = new QueryRunner(); //开发通用的DML,针对任意表public int update(String sql,Object... parameter){Connection connection = null; try {connection = JDBCUtilsByDruid.getConnection(); return queryRunner.update(connection, sql, parameter); } catch (SQLException e) {throw new RuntimeException(e); //将编译异常转化成运行异常,可以被捕获,也可以被抛出}finally {JDBCUtilsByDruid.close(null,null,connection); }}/**返回多个对象(多行结果)** @param sqlsql语句,可以存在？* @param clazz传入一个类的class对象例如Actor.class* @param parameter 传入?号具体的值,可以有多个* @return根据类似Actor.class类型,返回对应的ArrayList集合*/public List QueryMultiply(String sql,Class clazz, Object... parameter){Connection connection = null; try {connection = JDBCUtilsByDruid.getConnection(); return queryRunner.query(connection,sql,new BeanListHandler(clazz),parameter); } catch (SQLException e) {throw new RuntimeException(e); //将编译异常转化成运行异常,可以被捕获,也可以被抛出}finally {JDBCUtilsByDruid.close(null,null,connection); }}//返回单个对象(单行数据)public T querySingle(String sql,Class clazz,Object... parameter){Connection connection = null; try {connection = JDBCUtilsByDruid.getConnection(); return queryRunner.query(connection,sql,new BeanHandler(clazz),parameter); } catch (SQLException e) {throw new RuntimeException(e); //将编译异常转化成运行异常,可以被捕获,也可以被抛出}finally {JDBCUtilsByDruid.close(null,null,connection); }}//返回单个对象的单个属性(单行中的单列)public Object queryScalar(String sql,Object... parameter){Connection connection = null; try {connection = JDBCUtilsByDruid.getConnection(); return queryRunner.query(connection,sql,new ScalarHandler(),parameter); } catch (SQLException e) {throw new RuntimeException(e); //将编译异常转化成运行异常,可以被捕获,也可以被抛出}finally {JDBCUtilsByDruid.close(null,null,connection); }}}

13.2 domain中的类

public class Actor { //Javabean, POJO, Domain对象private Integer id; private String name; private String sex; private Date borndate; private String phone; public Actor() { //一定要给一个无参构造器[反射需要]}public Actor(Integer id, String name, String sex, Date borndate, String phone) {this.id = id; this.name = name; this.sex = sex; this.borndate = borndate; this.phone = phone; }public Integer getId() { return id; }public void setId(Integer id) { this.id = id; }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 Date getBorndate() { return borndate; }public void setBorndate(Date borndate) { this.borndate = borndate; }public String getPhone() { return phone; }public void setPhone(String phone) { this.phone = phone; }@Overridepublic String toString() {return "\nActor{" + "id=" + id + ", name='" + name + '\'' +", sex='" + sex + '\'' + ", borndate=" + borndate +", phone='" + phone + '\'' + '}'; }}

ActorDAO类继承BasicDAO类，这样的类可以有很多。

public class ActorDAO extends BasicDAO {}

13.3 测试类

public class TestDAO {@Test//测试ActorDAO对actor表的操作public void testActorDAO() {ActorDAO actorDAO = new ActorDAO(); //1.查询多行List actors = actorDAO.QueryMultiply("select * from actor where id >= ?", Actor.class, 1); System.out.println(actors); //2.查询单行Actor actor = actorDAO.querySingle("select * from actor where id = ?", Actor.class, 1); System.out.println(actor); //3.查询单行单个数据Object o = actorDAO.queryScalar("select name from actor where id = ?", 1); System.out.println(o); //4.DML操作当前演示updateint affectedRow = actorDAO.update("update actor set phone = ? where id = ?", "120", 3); System.out.println(affectedRow > 0 ? "OK" : "NO"); }}

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