Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之05.JDBC MetaData

最新推荐文章于 2025-08-24 11:06:10 发布

weixin_33968104

最新推荐文章于 2025-08-24 11:06:10 发布

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文章标签： java 数据库

本文链接：https://blog.youkuaiyun.com/weixin_33968104/article/details/85142640

本文介绍了JDBC中两种元数据的使用方法：结果集的元数据和数据库的元数据。通过示例代码展示了如何获取列名和类型等信息。

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JDBC MetaData有两种：
• 结果集的MetaData
• 数据库的MetaData

#####################Michael分割线#########################

结果集的MetaData
• ResultSet的getMetaData方法返回结果集元数据对象ResultSetMetaData

ConnectionUtil.java

package com.michael.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

public class ConnectionUtil {
         //第一种方法
         public Connection getConnection(){
                Connection conn = null;
                 try {
                         //Class.forName加载驱动
                        Class.forName( "com.mysql.jdbc.Driver");
                         //DriverManager获得连接
                        conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/jdbc_db","root","mysqladmin");
                        return conn;
                } catch (Exception e) {
                        e.printStackTrace();
                }
                return null;
        }
        //第二种方法
        public Connection getConnection(String driver,String url,String user,String password){
                Connection conn = null;
                try {
                        //Class.forName加载驱动
                        Class.forName(driver);
                        //DriverManager获得连接
                        conn = DriverManager.getConnection(url,user,password);
                        return conn;
                } catch (Exception e) {
                        e.printStackTrace();
                }
                return null;
        }
        //第三种方法
        public Connection openConnection(){
                String driver = "";
                String url = "";
                String user = "";
                String password = "";
                Properties prop = new Properties();
                Connection conn = null;
                try {
                        //加载属性文件
                        prop.load(this.getClass().getClassLoader().getResourceAsStream("DBConfig.properties"));
                        driver = prop.getProperty("driver");
                        url = prop.getProperty("url");
                        user = prop.getProperty("user");
                        password = prop.getProperty("password");
                        //Class.forName加载驱动
                        Class.forName(driver);
                        //DriverManager获得连接
                        conn = DriverManager.getConnection(url,user,password);
                        return conn;
                } catch (Exception e) {
                        e.printStackTrace();
                }
                return null;
        }

}

TestMetaData.java

package com.michael.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

public class TestMetaData {
         public static void test(){
                Connection conn = new ConnectionUtil().openConnection();
                 try {
                        Statement stmt = conn.createStatement();
                        String sql = "select * from CustomerTbl";
                        ResultSet rs = stmt.executeQuery(sql);
                        ResultSetMetaData rsmd = rs.getMetaData();
                         int columns = rsmd.getColumnCount();
                         for ( int i=1;i<=columns;i++){
                                String name = rsmd.getColumnName(i);
                                 int type = rsmd.getColumnType(i);
                                System.out.println(name+ ":"+type);
                        }
                } catch (SQLException e) {
                        e.printStackTrace();
                } finally{
                                 try {
                                        conn.close();
                                } catch (SQLException e) {
                                        e.printStackTrace();
                                }
                }
        }
}

Main.java

package com.michael.main;

import com.michael.jdbc.TestMetaData;

public class Main {

         /**
         * @param args
         */
         public static void main(String[] args) {
                TestMetaData.test();
        }
}

数据库的MetaData
• 通过数据库连接的getMetaData方法可以获得数据库连接的对象实例DatabaseMetaData

TestMetaData.java

package com.michael.jdbc;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;

public class TestMetaData {
         public static void test(){
                Connection conn = new ConnectionUtil().openConnection();
                 try {
                        DatabaseMetaData dbmd = conn.getMetaData();
                        System.out.println(dbmd.getDatabaseProductName());
                        System.out.println(dbmd.getDatabaseMajorVersion());
                } catch (SQLException e1) {
                        e1.printStackTrace();
                } finally{
                         try {
                                conn.close();
                        } catch (SQLException e) {
                                e.printStackTrace();
                        }
                }
                 /*
                try {
                        Statement stmt = conn.createStatement();
                        String sql = "select * from CustomerTbl";
                        ResultSet rs = stmt.executeQuery(sql);
                        ResultSetMetaData rsmd = rs.getMetaData();
                        int columns = rsmd.getColumnCount();
                        for (int i=1;i<=columns;i++){
                                String name = rsmd.getColumnName(i);
                                int type = rsmd.getColumnType(i);
                                System.out.println(name+":"+type);
                        }
                } catch (SQLException e) {
                        e.printStackTrace();
                }finally{
                                try {
                                        conn.close();
                                } catch (SQLException e) {
                                        e.printStackTrace();
                                }
                }
                */
        }
}