JDBC对分类表的增删改查

 package jdbc;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import org.junit.Test;public class jdbc_demo1 {@Testpublic void demo1(){Connection conn=null;PreparedStatement pstmt=null;ResultSet rs=null;try{//1、注册驱动Class.forName("com.mysql.jdbc.Driver");//2、获得连接conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/wh","root","1234");//3.创建执行SQL的对象String sql="select * from category";pstmt=conn.prepareStatement(sql);//4、向数据库发送sql,获得返回的结果集rs= pstmt.executeQuery();while (rs.next()) {System.out.println(rs.getInt("cid")+"  "+rs.getString("cname"));}}catch(Exception e){e.printStackTrace(); }finally{//4、释放资源if(rs!=null){  try{rs.close();}catch(SQLException e){e.printStackTrace();}rs=null;}if(pstmt!=null){  try{pstmt.close();}catch(SQLException e){e.printStackTrace();}pstmt=null;}if(conn!=null){  try{conn.close();}catch(SQLException e){e.printStackTrace();}conn=null;}}}}

工具累的抽取：

package jdbc.utils;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import com.mysql.jdbc.Statement;public class JDBCUtils {public static void loadDriver(){try {Class.forName("com.mysql.jdbc.Driver");} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static Connection getConnection(){Connection conn=null;try {loadDriver();   conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/wh","root","1234");} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}return conn;}public static void release(ResultSet rs,PreparedStatement stmt,Connection conn ){if(rs!=null){  try{rs.close();}catch(SQLException e){e.printStackTrace();}rs=null;}if(stmt!=null){  try{stmt.close();}catch(SQLException e){e.printStackTrace();}stmt=null;}if(conn!=null){  try{conn.close();}catch(SQLException e){e.printStackTrace();}conn=null;}}public static void release(Statement stmt,Connection conn ){if(stmt!=null){  try{stmt.close();}catch(SQLException e){e.printStackTrace();}stmt=null;}if(conn!=null){  try{conn.close();}catch(SQLException e){e.printStackTrace();}conn=null;}}}

package jdbc.utils;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.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.Properties;import com.mysql.jdbc.Statement;public class JDBCUtils { private static final String Drivername; private static final String url; private static final String usename; private static final String password; static{ //渎属性文件 Properties  properties=null ;try { InputStream is = new FileInputStream("src/jdbc.properties"); properties =new Properties(); properties.load(is);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();} Drivername= properties.getProperty("Drivername"); url=properties.getProperty("url"); usename=properties.getProperty("usename"); password=  properties.getProperty("password"); }public static void loadDriver(){try {Class.forName(Drivername);} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static Connection getConnection(){Connection conn=null;try { loadDriver();   conn=DriverManager.getConnection(url,usename,password);} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}return conn;}public static void release(ResultSet rs,PreparedStatement stmt,Connection conn ){if(rs!=null){  try{rs.close();}catch(SQLException e){e.printStackTrace();}rs=null;}if(stmt!=null){  try{stmt.close();}catch(SQLException e){e.printStackTrace();}stmt=null;}if(conn!=null){  try{conn.close();}catch(SQLException e){e.printStackTrace();}conn=null;}}public static void release(Statement stmt,Connection conn ){if(stmt!=null){  try{stmt.close();}catch(SQLException e){e.printStackTrace();}stmt=null;}if(conn!=null){  try{conn.close();}catch(SQLException e){e.printStackTrace();}conn=null;}}}

增添改查