java的result類-java中的resultset類詳解

java的result類_java中的resultset類詳解?：JDBCsun：提供了?套通?性的接?：可以連接任何的數(shù)據(jù)庫：連接數(shù)據(jù)庫的具體得到實例，具體的數(shù)據(jù)庫?商實現(xiàn)的。連接數(shù)據(jù)的步驟(別忘了復(fù)制jar包):(1)注冊驅(qū)動：Class.forName()：DriverManager(2)獲得鏈接對象：Connection(3)創(chuàng)建sql容器：語句：(4)執(zhí)?sql語句::stmt(5)查詢操作：遍歷結(jié)果集：ResultSet(6)關(guān)閉資源：ResultSet：詳解(更多可以看API)封裝了結(jié)果集的對象：內(nèi)部有?個可移動的光標(biāo)，默認(rèn)情況，指向第?條記錄集的上?條記錄：next();光標(biāo)下移動?次：返回的boolean的值;判斷是否有結(jié)果可以被遍歷：previous();光標(biāo)上移動?次：last()移動到最后??：afterLast();移動到最后??之后：beforeFirst()移動到第??的之前：first()getObject();getInt();的GetString();getFloat();getDouble()getDate();getXxx()的的getMetaData()獲得結(jié)果集的元數(shù)據(jù):(重要)packagecom.yidongxueyuan.dao;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.ResultSet;importjava.sql.SQLException;importjava.sql.Statement;publicclassStudentDaoImpl{

publicstaticvoidmain(String[]args){try{Class.forName("com.mysql.jdbc.Driver");Connectionconn=DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbc01","root","root");Statementstmt=conn.createStatement();Stringsql="select*fromstudent";ResultSetrs=stmt.executeQuery(sql);/*while(rs.next()){intid=rs.getInt("sid");Stringname=rs.getString("sname");System.out.println(id+""+name);}*/rs.next();//上移動?次：//rs.previous();//rs.last();//rs.first();rs.beforeFirst();while(rs.next()){//Objectobject=rs.getObject("1");intid=rs.getInt("sid");Stringname=rs.getString("sname");System.out.println(id+""+name);}rs.close();stmt.close();conn.close();}catch(ClassNotFoundExceptione){e.printStackTrace();}catch(SQLExceptione){e.printStackTrace();}finally{}

}}//mysql封裝：?具類：封裝好的UTIL：packagecom.yidongxueyuan.dao;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.ResultSet;importjava.sql.SQLException;importjava.sql.Statement;/**對JDBC進(jìn)?封裝：*/publicclassJdbcUtils2{//準(zhǔn)備數(shù)據(jù)庫的四?參數(shù)：privatestaticfinalStringdriver="com.mysql.jdbc.Driver";privatestaticfinalStringurl="jdbc:mysql://localhost:3306/jdbc01";privatestaticfinalStringusername="root";privatestaticfinalStringpassword="root";/**驅(qū)動：只需要注冊?次就OK**/static{try{Class.forName(driver);}catch(ClassNotFoundExceptione){e.printStackTrace();}}/**1：創(chuàng)建?具類：直接獲得?個連接對象：*/publicstaticConnectiongetConnection(){

try{Connectionconnection=DriverManager.getConnection(url,username,password);returnconnection;}catch(SQLExceptione){thrownewRuntimeException(e);}}/**定義?個?法：釋放資源：直接將rsstmtconn全部釋放：*/publicstaticvoidrelease(ResultSetrs,Statementstmt,Connectionconn){if(rs!=null){try{rs.close();}catch(SQLExceptione){e.printStackTrace();}rs=null;}if(stmt!=null){try{stmt.close();}catch(SQLExceptione){e.printStackTrace();}stmt=null;}if(conn!=null){try{conn.close();}catch(SQLExceptione){e.printStackTrace();}conn=null;

}}}調(diào)??具類實現(xiàn)操作：packagecom.yidongxueyuan.dao;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.ResultSet;importjava.sql.SQLException;importjava.sql.Statement;/**使??具類：對代碼進(jìn)?重構(gòu)：*/publicclassStudentDaoImpl2{publicstaticvoidmain(String[]args){Connectionconn=null;Statementstmt=null;ResultSetrs=null;try{//使??具類獲得?個連接對象：conn=JdbcUtils2.getConnection();stmt=conn.createStatement();Stringsql="select*fromstudent";rs=stmt.executeQuery(sql);while(rs.next()){//Objectobject=rs.getObject("1");intid=rs.getInt("sid");Stringname=rs.getString("sname");System.out.println(id+""+name);}}catch(SQLExceptione){e.printStackTrace();}finally{JdbcUtils2.release(rs,stmt,conn);

}}}上?的代碼是硬編碼，如果是軟編碼的話步驟如下：1個???件內(nèi)容：#thisismymysqlconfigurationdriver=com.mysql.jdbc.Driverurl=jdbc:mysql://localhost:3306/jdbc01username=rootpassword=root2jdbcutil.java讀取如下：packagecom.yidongxueyuan.dao;importjava.io.IOException;importjava.io.InputStream;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.ResultSet;importjava.sql.SQLException;importjava.sql.Statement;importjava.util.Properties;/**讀取外部的配置?件*/publicclassJdbcUtil{privatestaticfinalPropertiesp=newProperties();privatestaticStringurl;privatestaticStringdriver;privatestaticStringusername;privatestaticStringpassword;static{try{//將外部的配置?件進(jìn)?讀?。侯惖募虞d器：InputStreamin=JdbcUtil.class.getClassLoader().getResourceAsStream("perties");p.load(in);

driver=p.getProperty("driver");Class.forName(driver);}catch(IOExceptione){e.printStackTrace();}catch(ClassNotFoundExceptione){e.printStackTrace();}}/**1：創(chuàng)建?具類：直接獲得?個連接對象：*/publicstaticConnectiongetConnection(){try{url=p.getProperty("url");username=p.getProperty("username");password=p.getProperty("password");//Connectionconnection=DriverManager.getConnection(url,username,password);returnconnection;}catch(SQLExceptione){thrownewRuntimeException(e);}}//釋放連接：/**定義?個?法：釋放資源：直接將rsstmtconn全部釋放：*/publicstaticvoidrelease(ResultSetrs,Statementstmt,Connectionconn){if(rs!=null){try{rs.close();}catch(SQLExceptione){e.printStackTrace();}rs=null;

}if(stmt!=null){try{stmt.close();}catch(SQLExceptione){e.printStackTrace();}stmt=null;}if(conn!=null){try{conn.close();}catch(SQLExceptione){e.printStackTrace();}conn=null;}}/*publicstaticvoidmain(String[]args){Connectionconnection=getConnection();System.out.println(connection);}*/}使?上?的?具類完成增加改查操作：packagecom.yidongxueyuan.dao2;importjava.sql.Connection;importjava.sql.Statement;importjava.util.Date;importorg.junit.Test;importcom.yidongxueyuan.dao.JdbcUtil;publicclassStudentCRUD{//insert插?：@TestpublicvoidinsertStudent()throwsException{

Connectionconn=JdbcUtil.getConnection();Statementstmt=conn.createStatement();intnum=stmt.executeUpdate("insertintostudent(sname,birthday)"+"values('xxx','"+newjava.sql.Date(System.currentTimeMillis())+"')");if(num>0){System.out.println("插?成功");}else{System.out.println("插?失敗");}JdbcUtil.release(null,stmt,conn);}//刪除：@TestpublicvoiddeleteStudent()throwsException{Connectionconn=JdbcUtil.getConnection