jdbc简介
jdbc全称为:java data base connectivity (java数据库连接),可以为多种数据库提供填统一的访问。jdbc是sun开发的一套数据库访问编程接口,是一种sql级的api。它是由java语言编写完成,所以具有很好的跨平台特性,使用jdbc编写的数据库应用程序可以在任何支持java的平台上运行,而不必在不同的平台上编写不同的应用程序。
jdbc编程步骤
(1)加载驱动程序:
下载驱动包 : http://dev.mysql.com/downloads/connector/j/
解压,得到 jar文件。将该文件复制到java工程目录java resources/libraries/ 下,→ buildpath 。
(2)获得数据库连接
(3)创建statement对象:
(4)向数据库发送sql命令
(5)处理数据库的返回结果(resultset类)
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package com.baidu.emp.jdbctest; import java.sql.connection; import java.sql.drivermanager; import java.sql.resultset; import java.sql.statement; import com.mysql.jdbc.driver; /** * 开始使用jdbc连接数据库 * @author admin * */ public class test001 { public static void main(string[] args) throws exception { /** * 加载驱动 */ // 方法一: /* * import java.sql.drivermanager; import com.mysql.jdbc.driver; */ // driver driver = new driver(); // drivermanager.registerdriver(driver); // 方法二:(推荐使用) class.forname("com.mysql.jdbc.driver"); /** * 创建链接 */ string url = "jdbc:mysql://localhost:3306/testjdbc"; string user = "root"; string password = "root"; connection connection = drivermanager.getconnection(url, user, password); // 创建statement对象 statement statement = connection.createstatement(); /** * 执行sql,获取结果集 */ string sql = "select * from test01"; resultset result = statement.executequery(sql); // 遍历结果集 while (result.next()) { string name = result.getstring("name"); int id = result.getint("id"); system.out.println(name + "\t" + id); } /** * 关闭链接,释放资源 */ result.close(); statement.close(); connection.close(); } } |
防止sql注入改用preparestatement
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package com.boya.emp.jdbctest; import java.sql.connection; import java.sql.drivermanager; import java.sql.preparedstatement; import java.sql.resultset; /** * sql注入,使用preparestatement对象进行预编译 * @author admin * */ public class test002 { public static void main(string[] args) throws exception { /** * 加载驱动 */ class .forname( "com.mysql.jdbc.driver" ); /** * 创建链接 */ string url = "jdbc:mysql://localhost:3306/testjdbc" ; string user = "root" ; string password = "root" ; connection connection = drivermanager.getconnection(url, user, password); // 写sql string sql = "select * from test01 where id = ?" ; //创建statement对象,预编译 preparedstatement statement = connection.preparestatement(sql); //设置参数 statement.setint( 1 , 2 ); /** * 执行sql,获取结果集 */ resultset result = statement.executequery(); // 遍历结果集 while (result.next()) { string name = result.getstring( "name" ); int id = result.getint( "id" ); system.out.println(name + "\t" + id); } /** * 关闭链接,释放资源 */ result.close(); statement.close(); connection.close(); } } |
进行代码优化,设置配置文件,工具类,实现增删该查
增加配置文件方便修改数据库,用户登录。。。
jdbc.properties(配置文件名)
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drivername=com.mysql.jdbc.driver url=jdbc:mysql: //localhost:3306/testjdbc username=root password=root |
注意写配置文件时中间不可以有空格,引号之类的
工具类:增强了代码的复用性
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package com.baidu.emp.utils; import java.io.inputstream; import java.sql.connection; import java.sql.drivermanager; import java.sql.preparedstatement; import java.sql.resultset; import java.sql.sqlexception; import java.util.properties; import org.junit.test; public class jdbcutils { static string driverclassname; static string url; static string user; static string password; static { // 创建配置文件对象 properties properties = new properties(); // 加载配置文件输入流 inputstream inputstream = jdbcutils. class .getclassloader().getresourceasstream( "jdbc.properties" ); // 重新加载配置文件 try { properties.load(inputstream); // 获取配置文件的值 driverclassname = properties.getproperty( "drivername" ); url = properties.getproperty( "url" ); user = properties.getproperty( "username" ); password = properties.getproperty( "password" ); class .forname(driverclassname); } catch (exception e) { // 抛出异常 throw new runtimeexception(e); } } /** * 获取连接 */ @test public void testname() throws exception { system.out.println(driverclassname); } public static connection getconnection() { connection connection = null ; try { connection = drivermanager.getconnection(url, user, password); } catch (sqlexception e) { // 抛出异常 throw new runtimeexception(e); } return connection; } /** * 关闭链接,释放资源 */ public static void close(connection connection, preparedstatement statement, resultset resultset) { try { if (resultset != null ) { resultset.close(); } resultset = null ; // 垃圾及时清除 //注意,不要弄成死循环 close(connection, statement); } catch (sqlexception e) { throw new runtimeexception(e); } } /** * 增删改释放资源 */ public static void close(connection connection, preparedstatement statement) { try { if (connection != null ) { connection.close(); } connection = null ; if (statement != null ) { statement.close(); } statement = null ; } catch (sqlexception e) { throw new runtimeexception(e); } } } |
测试增删改查:
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package com.baidu.emp.jdbctest; import java.sql.connection; import java.sql.preparedstatement; import java.sql.resultset; import org.junit.after; import org.junit.before; import org.junit.test; import com.baidu.emp.utils.jdbcutils; /** * 使用jdbcutils连接数据库进行增删改查 * * @author admin * */ public class test003 { // 初始化值 connection connection = null ; preparedstatement statement = null ; resultset result = null ; @before public void start() throws exception { // 创建链接 connection = jdbcutils.getconnection(); system.out.println( "创建链接" ); } @after public void end() throws exception { // 关闭链接 jdbcutils.close(connection, statement, result); system.out.println( "关闭链接" ); } /** *插入数据 * @throws exception */ @test public void add() throws exception { string sql = "insert into test01 values(null,?)" ; statement = connection.preparestatement(sql); statement.setstring( 1 , "李四" ); int result = statement.executeupdate(); if (result!= 0 ) { system.out.println( "添加成功" ); } } /** * 删除数据 * @throws exception */ @test public void del() throws exception { string sql = "delete from test01 where id =?" ; statement = connection.preparestatement(sql); statement.setint( 1 , 3 ); int result = statement.executeupdate(); if (result!= 0 ) { system.out.println( "删除成功" ); } } /** * 修改数据 * @throws exception */ @test public void change() throws exception { string sql = "update test01 set name = ? where id = ?" ; statement = connection.preparestatement(sql); statement.setstring( 1 , "张飞" ); statement.setint( 2 , 2 ); int result = statement.executeupdate(); if (result!= 0 ) { system.out.println( "修改成功" ); } } /** * 查询全部数据 * @throws exception */ @test public void findall() throws exception { string sql = "select id , name from test01" ; statement = connection.preparestatement(sql); result = statement.executequery(); if (result.next()) { system.out.println( "查询成功" ); } } /** * 条件查询数据 * @throws exception */ @test public void findone() throws exception { string sql = "select id , name from test01 where id = ?" ; statement = connection.preparestatement(sql); statement.setint( 1 , 2 ); result = statement.executequery(); if (result.next()) { system.out.println( "查询成功" ); } } } |
以上就是相关知识以及相关代码,感谢大家对服务器之家的支持。