Java程序訪問數(shù)據(jù)庫：

• 1、獲取數(shù)據(jù)庫廠商提供的驅動（jdbc接口的實現(xiàn)類）

如ojdbc14.jar——Oracle數(shù)據(jù)庫驅動jar包

mysql-connector-java-5.1.8-bin.jar——MySQL數(shù)據(jù)庫驅動jar包

自己去網(wǎng)上下載就行。

• 2、使用JDBC的API訪問數(shù)據(jù)庫

連接、SQL語句執(zhí)行、結果

java.sql.Driver：各個數(shù)據(jù)庫廠商需要實現(xiàn)該接口，驅動的標記

java.sql.Connection：封裝和數(shù)據(jù)庫的連接

java.sql.Statement：封裝需要執(zhí)行的SQL語句

java.sql.ResultSet：封裝查詢的結果集

• 3、JDBC編程步驟

step1——加載驅動

step2——獲取連接對象

step3——執(zhí)行SQL語句

step4——處理結果集

step5——關閉資源

• 4、下面給出連接數(shù)據(jù)庫的工具類（自己寫的連接MySql數(shù)據(jù)庫，如要連接Oeacle可修改對應參數(shù)）

package com.day03;import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties;//加入Java開發(fā)交流君樣：756584822一起吹水聊天 public class ConnectionUtils {// 線程單例private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();private static String url;private static String driver;private static String username;private static String password;//加入Java開發(fā)交流君樣：756584822一起吹水聊天static {Properties props = new Properties();try {// 從屬性文件中讀取數(shù)據(jù)庫配置信息，以加載類的方式加載配置文件props.load(ConnectionUtils.class.getClassLoader().getResourceAsStream("com/day03/db_mysql.properties"));} catch (IOException e) {}if (props != null) {url = props.getProperty("url");driver = props.getProperty("driver");username = props.getProperty("username");password = props.getProperty("password");// 裝載并注冊數(shù)據(jù)庫驅動try {Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();}}}//加入Java開發(fā)交流君樣：756584822一起吹水聊天public static Connection getConnection() throws SQLException {Connection con = tl.get();if (con == null) {con = DriverManager.getConnection(url, username, password);tl.set(con);}return con;}public static void closeConnection() {Connection con = tl.get();try {if (con != null) {con.close();tl.set(null);}} catch (SQLException e) {e.printStackTrace();}}public static void closeStatement(Statement stmt) {try {if (stmt != null) {stmt.close();}} catch (SQLException e) {e.printStackTrace();}}public static void closeResultSet(ResultSet rs) {try {if (rs != null) {rs.close();}} catch (SQLException e) {e.printStackTrace();}}public static void closeAll(Statement stmt, ResultSet rs){closeConnection();closeStatement(stmt);closeResultSet(rs);}public static void main(String[] args) throws Exception{System.out.println(ConnectionUtils.getConnection());}}

5、配置參數(shù)文件db_mysql.properties

driver=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/test username=root password=root

6、Dao模式操作數(shù)據(jù)庫下面是代碼示例

1）Emp.java

//實體類 public class Emp {private int id;private String name;private double salary;public int getId() {return id;}@Overridepublic String toString() {return "Emp [id=" + id + ", name=" + name + ", salary=" + salary + "]";}//加入Java開發(fā)交流君樣：756584822一起吹水聊天public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}public Emp(int id, String name, double salary) {super();this.id = id;this.name = name;this.salary = salary;}public Emp() {super();}public Emp(String name, double salary) {super();this.name = name;this.salary = salary;} }

2)Dao接口類

import java.util.List;public interface EmpDao {List<Emp> findAllEmp() throws Exception; }

3）工廠類

public class EmpDaoFactory {// 讀取文件中實現(xiàn)類的類名，通過反射實例化public static EmpDao getEmpDao(){return new EmpDaoMySQL();} }

4）Dao接口實現(xiàn)類

public class EmpDaoMySQL implements EmpDao{public static final String FIND_ALL_EMP = "select * from t_emp";//查詢語句public List<Emp> findAllEmp() throws Exception{List<Emp> empList = new ArrayList<Emp>();Connection conn = ConnectionUtils.getConnection();PreparedStatement stmt = conn.prepareStatement(FIND_ALL_EMP);ResultSet rs = stmt.executeQuery();while(rs.next()){int id = rs.getInt(1);String name = rs.getString(2);double salary = rs.getDouble(3);Emp emp = new Emp(id, name, salary);empList.add(emp);}//加入Java開發(fā)交流君樣：756584822一起吹水聊天ConnectionUtils.closeAll(stmt, rs);return empList;} }

5）測試類

public class EmpBiz {public static void main(String[] args) throws Exception{EmpDao dao = EmpDaoFactory.getEmpDao();List<Emp> empList = dao.findAllEmp();for(Emp e : empList){System.out.println(e);}} } 創(chuàng)作挑戰(zhàn)賽新人創(chuàng)作獎勵來咯，堅持創(chuàng)作打卡瓜分現(xiàn)金大獎

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