Java JDBC 小例子详解编程语言

1. 使用MySQL建立一个test数据库，里面建立一个mytable表，3列（id，name，age）；将url, user, password配制成properties文件，放到 工程resource源代码包下面，这里将其命名为db_connect.properties文件

    url = jdbc:mysql://localhost:3306/test   
    user = root   
    password = admin  

2. 将数据库连接封装到一个类中，利用配置文件连接，静态返回connection

    package study.jdbc;   
       
    import java.io.FileInputStream;   
    import java.io.FileNotFoundException;   
    import java.io.IOException;   
    import java.io.InputStream;   
    import java.sql.Connection;   
    import java.sql.DriverManager;   
    import java.sql.SQLException;   
    import java.util.Properties;   
       
    public class DBConnect {   
        static String url;   
        static String user;   
        static String password;   
       
        /**  
         * 获取一个JDBC连接，返回一个Connection对象  
         * @return connection  
         */   
        public static Connection connectDB() {   
            Connection connection = null;   
            readProperties();   
            try {   
                Class.forName("com.mysql.jdbc.Driver");   
                connection = DriverManager.getConnection(url, user, password);   
            } catch (SQLException e) {   
                e.printStackTrace();   
            } catch (ClassNotFoundException e) {   
                e.printStackTrace();   
            }   
            return connection;   
        }   
       
        /**  
         * 读取properties文件，获取url,user,password  
         */   
        private static void readProperties() {   
            String fileName = "resouce/db_connect.properties"; //相对于工程   
            Properties properties = new Properties();   
            try {   
                InputStream in = new FileInputStream(fileName);   
                properties.load(in);   
                in.close();   
            } catch (FileNotFoundException e) {   
                e.printStackTrace();   
            } catch (IOException e) {   
                e.printStackTrace();   
            }   
            url = properties.getProperty("url");   
            user = properties.getProperty("user");   
            password = properties.getProperty("password");   
        }   
       
    }  

3.  对数据库进行增删改查的测试，主要练习使用PreparedStatement

    package study.jdbc;   
       
    import java.sql.Connection;   
    import java.sql.PreparedStatement;   
    import java.sql.ResultSet;   
    import java.sql.SQLException;   
       
    public class TestMain {   
        public static void main(String[] args) {   
            Connection connection = DBConnect.connectDB(); //获取数据库连接   
            TestMain test = new TestMain();   
            try { //测试   
                test.clear(connection);    
                test.insert(connection); //增   
                test.query(connection);   
                System.out.println("----------");   
                test.delete(connection); //删     
                test.query(connection);     
                System.out.println("----------");   
                test.update(connection); //改   
                test.query(connection);  //查   
                connection.close(); //关闭数据库连接   
            } catch (SQLException e) {   
                e.printStackTrace();   
            }   
        }   
           
        /**  
         * 使用PreparedStatement，效率高  
         * 动态执行SQL(带参数的SQL语句),是Statement子接口  
         * 对数据库进行insert，用带参数的语句批量插入  
         * @param connection  
         * @throws SQLException  
         */   
        public void insert(Connection connection) throws SQLException {   
            String sql = "INSERT INTO mytable(id,name,age) values (?,?,22);";   
            PreparedStatement pr = connection.prepareStatement(sql);   
            for (int i = 1; i <= 3; i++) {   
                pr.setInt(1, i);   
                pr.setString(2, "demo"+i);   
                pr.executeUpdate();   
            }   
        }   
       
        /**  
         * 对数据库进行delete  
         * @param connection  
         * @throws SQLException  
         */   
        public void delete(Connection connection) throws SQLException {   
            String sql = "delete from mytable where id=2;";   
            PreparedStatement pr = connection.prepareStatement(sql);   
            pr.executeUpdate();   
        }   
       
        /**  
         * 对数据库进行update  
         * @param connection  
         * @throws SQLException  
         */   
        public void update(Connection connection) throws SQLException {   
            String sql = "UPDATE mytable SET name='new' WHERE id=1;";   
            PreparedStatement pr = connection.prepareStatement(sql); // 创建statement对象发送SQL到数据库   
            pr.executeUpdate(); // 执行UPDATE   
       
        }   
       
        /**  
         * 查询query遍历结果集  
         * @param connection  
         * @throws SQLException  
         */   
        public void query(Connection connection) throws SQLException {   
            String sql = "select * from mytable;";   
            PreparedStatement st = connection.prepareStatement(sql);   
            ResultSet re = st.executeQuery(); // 查询，返回单个ResultSet对象   
            while (re.next()) {   
                int id = re.getInt(1);   
                String name = re.getString(2);   
                int age = re.getInt(3);   
                System.out.println(id + "/t" + name + "/t" + age);   
            }// 遍历结果集   
        }   
           
        /**  
         * 清空表  
         * @param connection  
         * @throws SQLException  
         */   
        public void clear(Connection connection) throws SQLException {   
            String sql = "delete from mytable;";   
            PreparedStatement pr = connection.prepareStatement(sql);   
            pr.executeUpdate();   
        }   
    }