Java JDBC 小例子

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,password);  
            } catch (SQLException e) {  
                e.printStackTrace();  
            } catch (ClassNotFoundException e) {  
                e.printStackTrace();  
            }  
            return connection;  
        }  
      
        /** 
         * 读取properties文件，获取url,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();  
        }  
    }