jdbc簡介
jdbc全稱為：java data base connectivity (java數(shù)據(jù)庫連接），可以為多種數(shù)據(jù)庫提供填統(tǒng)一的訪問。jdbc是sun開發(fā)的一套數(shù)據(jù)庫訪問編程接口，是一種sql級的api。它是由java語言編寫完成，所以具有很好的跨平臺特性，使用jdbc編寫的數(shù)據(jù)庫應(yīng)用程序可以在任何支持java的平臺上運(yùn)行，而不必在不同的平臺上編寫不同的應(yīng)用程序。
jdbc編程步驟
（1）加載驅(qū)動程序：
下載驅(qū)動包 : http://dev.mysql.com/downloads/connector/j/
解壓，得到 jar文件。將該文件復(fù)制到j(luò)ava工程目錄java resources/libraries/ 下，→ buildpath 。
（2）獲得數(shù)據(jù)庫連接
（3）創(chuàng)建statement對象：
（4）向數(shù)據(jù)庫發(fā)送sql命令
（5）處理數(shù)據(jù)庫的返回結(jié)果(resultset類)
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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;/** * 開始使用jdbc連接數(shù)據(jù)庫 * @author admin * */public class test001 { public static void main(string[] args) throws exception { /** * 加載驅(qū)動 */ // 方法一： /* * import java.sql.drivermanager; import com.mysql.jdbc.driver; */ // driver driver = new driver(); // drivermanager.registerdriver(driver); // 方法二：(推薦使用) class.forname("com.mysql.jdbc.driver"); /** * 創(chuàng)建鏈接 */ string url = "jdbc:mysql://localhost:3306/testjdbc"; string user = "root"; string password = "root"; connection connection = drivermanager.getconnection(url, user, password); // 創(chuàng)建statement對象 statement statement = connection.createstatement(); /** * 執(zhí)行sql，獲取結(jié)果集 */ string sql = "select * from test01"; resultset result = statement.executequery(sql); // 遍歷結(jié)果集 while (result.next()) { string name = result.getstring("name"); int id = result.getint("id"); system.out.println(name + "\t" + id); } /** * 關(guān)閉鏈接，釋放資源 */ 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對象進(jìn)行預(yù)編譯 * @author admin * */public class test002 { public static void main(string[] args) throws exception { /** * 加載驅(qū)動 */ class.forname("com.mysql.jdbc.driver"); /** * 創(chuàng)建鏈接 */ string url = "jdbc:mysql://localhost:3306/testjdbc"; string user = "root"; string password = "root"; connection connection = drivermanager.getconnection(url, user, password); // 寫sql string sql = "select * from test01 where id = ?"; //創(chuàng)建statement對象，預(yù)編譯 preparedstatement statement = connection.preparestatement(sql); //設(shè)置參數(shù) statement.setint(1, 2); /** * 執(zhí)行sql，獲取結(jié)果集 */ resultset result = statement.executequery(); // 遍歷結(jié)果集 while (result.next()) { string name = result.getstring("name"); int id = result.getint("id"); system.out.println(name + "\t" + id); } /** * 關(guān)閉鏈接，釋放資源 */ result.close(); statement.close(); connection.close(); }} |
進(jìn)行代碼優(yōu)化，設(shè)置配置文件，工具類，實現(xiàn)增刪該查
增加配置文件方便修改數(shù)據(jù)庫，用戶登錄。。。
jdbc.properties(配置文件名)
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drivername=com.mysql.jdbc.driverurl=jdbc:mysql://localhost:3306/testjdbcusername=rootpassword=root |
注意寫配置文件時中間不可以有空格，引號之類的
工具類：增強(qiáng)了代碼的復(fù)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 { // 創(chuàng)建配置文件對象 properties properties = new properties(); // 加載配置文件輸入流 inputstream inputstream = jdbcutils.class.getclassloader().getresourceasstream("jdbc.properties"); // 重新加載配置文件 try { properties.load(inputstream); // 獲取配置文件的值 driverclassname = properties.getproperty("drivername"); url = properties.getproperty("url"); user = properties.getproperty("username"); password = properties.getproperty("password"); class.forname(driverclassname); } catch (exception e) { // 拋出異常 throw new runtimeexception(e); } } /** * 獲取連接 */ @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) { // 拋出異常 throw new runtimeexception(e); } return connection; } /** * 關(guān)閉鏈接，釋放資源 */ public static void close(connection connection, preparedstatement statement, resultset resultset) { try { if (resultset != null) { resultset.close(); } resultset = null; // 垃圾及時清除 //注意，不要弄成死循環(huán) close(connection, statement); } catch (sqlexception e) { throw new runtimeexception(e); } } /** * 增刪改釋放資源 */ 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); } } } |
測試增刪改查：
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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連接數(shù)據(jù)庫進(jìn)行增刪改查 * * @author admin * */public class test003 { // 初始化值 connection connection = null; preparedstatement statement = null; resultset result = null; @before public void start() throws exception { // 創(chuàng)建鏈接 connection = jdbcutils.getconnection(); system.out.println("創(chuàng)建鏈接"); } @after public void end() throws exception { // 關(guān)閉鏈接 jdbcutils.close(connection, statement, result); system.out.println("關(guān)閉鏈接"); } /** *插入數(shù)據(jù) * @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"); } } /** * 刪除數(shù)據(jù) * @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("刪除成功"); } } /** * 修改數(shù)據(jù) * @throws exception */ @test public void change() throws exception { string sql = "update test01 set name = ? where id = ?"; statement = connection.preparestatement(sql); statement.setstring(1, "張飛"); statement.setint(2, 2); int result = statement.executeupdate(); if (result!=0) { system.out.println("修改成功"); } } /** * 查詢?nèi)繑?shù)據(jù) * @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("查詢成功"); } } /** * 條件查詢數(shù)據(jù) * @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("查詢成功"); } } } |
以上就是相關(guān)知識以及相關(guān)代碼，感謝大家對服務(wù)器之家的支持。
