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【第17章：Java数据库编程】_使用元数据分析数据库

发布时间：2021-01-12 18:35:26编辑：雪饮阅读（）

 用DatabaseMetaData获取数据库元数据与表元数据

import java.sql.Connection ;
import java.sql.DriverManager ;
import java.sql.DatabaseMetaData ;
import java.sql.ResultSet ;
public class Hello{
       public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
       public static final String DBURL = "jdbc:mysql://localhost:3306/xynes" ;
       public static final String DBUSER = "root" ;
       public static final String DBPASS = "" ;
       public static void main(String args[]) throws Exception{
              Class.forName(DBDRIVER) ;
            Connection conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS) ;
              DatabaseMetaData dmd=conn.getMetaData();
              System.out.println("数据库名称:"+dmd.getDatabaseProductName());
              System.out.println("数据库版本:"+dmd.getDatabaseMajorVersion()+"."+dmd.getDatabaseMinorVersion());
             
              ResultSet rs=dmd.getPrimaryKeys(null,null,"v9_admin") ;
              while(rs.next()){
                     System.out.println("表类别:"+ rs.getString(1)) ;
                     System.out.println("表模式:"+ rs.getString(2)) ;
                     System.out.println("表名称:"+ rs.getString(3)) ;
                     System.out.println("列名称:"+ rs.getString(4)) ;
                     System.out.println("主键序列号:"+ rs.getString(5)) ;
                     System.out.println("主键名称:"+ rs.getString(6)) ;
              }
              conn.close() ;
       }
};

用ResultSetMetaData获取结果集的元数据
import java.sql.Connection ;
import java.sql.DriverManager ;
import java.sql.ResultSetMetaData ;
import java.sql.PreparedStatement ;
public class Hello{
       public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
       public static final String DBURL = "jdbc:mysql://localhost:3306/xynes" ;
       public static final String DBUSER = "root" ;
       public static final String DBPASS = "" ;
       public static void main(String args[]) throws Exception{
              Class.forName(DBDRIVER) ;
            Connection conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS) ;
              String sql="select userid,username,password,roleid,encrypt,lastloginip from v9_admin";
              PreparedStatement pstmt = conn.prepareStatement(sql) ;
              ResultSetMetaData rsmd=pstmt.getMetaData() ;
              System.out.println("一共返回"+rsmd.getColumnCount()+"列数据");
              if(rsmd.isAutoIncrement(1) ){
                     System.out.println(rsmd.getColumnName(1)+"列是增长列");
              }
              conn.close() ;
       }
};
D:\>javac Hello.java
D:\>java Hello
一共返回6列数据
userid列是增长列