1.jdbc的概述

　　是sun公司統(tǒng)一提供的一套接口規(guī)范,各個(gè)數(shù)據(jù)庫生產(chǎn)商提供實(shí)現(xiàn)

　　注冊驅(qū)動,獲得連接,獲得執(zhí)行的SQL語句對象,釋放資源

package com.learn.jdbc;import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException;import org.junit.Test;public class Demo1 {Connection conn = null;@Testpublic void test() {try {//注冊驅(qū)動Class.forName("com.mysql.jdbc.Driver");//獲得連接String url = "jdbc:mysql///mydatebase";String user = "root";String password = "root";conn = DriverManager.getConnection(url, user, password);} catch (Exception e) {e.printStackTrace();//釋放資源if( conn != null) {try {conn.close();} catch (SQLException e1) {e1.printStackTrace();}//垃圾回收盡快回收對象conn = null;}}} }

2.JDBC的API

　　connection

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　　statement

3.JDBC的元數(shù)據(jù)MataDate(提高通用性較高的代碼)

• DatabaseMetaData：獲得數(shù)據(jù)庫連接的信息,獲得數(shù)據(jù)庫的表的信息.

* 獲得數(shù)據(jù)庫元數(shù)據(jù):Connection中g(shù)etMetaData();

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• ParameterMetaData：獲得SQL中的參數(shù)的個(gè)數(shù)及類型.

* 獲得參數(shù)元數(shù)據(jù)：PreparedStatement中g(shù)etParameterMetaData()

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• ResultSetMetaData：獲得結(jié)果集中的列名及列的類型.

* 獲得結(jié)果集元數(shù)據(jù)：ResultSet中g(shù)etMeta()

4.元數(shù)據(jù)的使用

public void demo2(){Connection conn = null;conn = JDBCUtils2.getConnection();// 獲得數(shù)據(jù)庫元數(shù)據(jù):try {DatabaseMetaData metaData = conn.getMetaData();System.out.println("獲得驅(qū)動名稱:"+metaData.getDriverName());System.out.println("獲得驅(qū)動URL:"+metaData.getURL());System.out.println("獲得用戶名:"+metaData.getUserName());// 獲得表中的主鍵：ResultSet rs = metaData.getPrimaryKeys(null, null, "category");if(rs.next()){String name = rs.getString("COLUMN_NAME");System.out.println(name);}} catch (SQLException e) {e.printStackTrace();}}

參數(shù)元數(shù)據(jù)

　　

public void demo3(){Connection conn = null;PreparedStatement stmt = null;try{conn = JDBCUtils2.getConnection();String sql = "update category set cname = ? where cid = ?";stmt = conn.prepareStatement(sql);ParameterMetaData metaData = stmt.getParameterMetaData();int count = metaData.getParameterCount();System.out.println(count);}catch(Exception e){}}

結(jié)果集元數(shù)據(jù)

public void demo4(){Connection conn = null;PreparedStatement stmt = null;ResultSet rs = null;try{conn = JDBCUtils2.getConnection();String sql = "select * from category";stmt = conn.prepareStatement(sql);rs = stmt.executeQuery();ResultSetMetaData metaData = rs.getMetaData();int count = metaData.getColumnCount();for(int i = 1;i<=count ;i++){String name = metaData.getColumnName(i);String type = metaData.getColumnTypeName(i);System.out.println(name+type);}}catch(Exception e){}}

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轉(zhuǎn)載于:https://www.cnblogs.com/learnjfm/p/6880663.html

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