项目中连接数据库，类的封装；

一.首先创建一个类，封装数据库和个人信息：

package com.yxq.dao;

public class Constants {
public static String url ="jdbc:mysql://127.0.0.1:3306/personblog";
public static String className="com.mysql.jdbc.Driver";
public static String userName ="root";
public static String password = "root";

}

以后只要修改这个类的信息；就可以了；

还要添加mysql-connector-java-5.0.8.jar 这个jar包到项目中；

先在网上下载这个jar，然后复制到项目WEB-INF目录下的lib文件夹中，在选中jar，右击，build path—> add bulid path;

二、封装一个类来连接数据库和关闭数据库：

package com.yxq.dao;
/*导入所需的包*/
import java.sql.Connection;//表示链接到某个数据库的链接;
import java.sql.DriverManager;//用来获取数据库链接的类;
import java.sql.ResultSet;//封装查询结果集的类;
import java.sql.SQLException;
//import java.sql.SQLException;//异常处理类;
import java.sql.Statement; //用来执行SQL语句的类;


public class DB {
    // 获取数据的连接；
    public static Connection getConnection() throws Exception{
        try{
            Class.forName(Constants.className);
            Connection con = DriverManager.getConnection(Constants.url,Constants.userName,Constants.password);
            return con;
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("连接失败");
            return null;
        }
        
    }
    // 关闭Statement对象;
    public static void closeStatement(Statement stmt) throws Exception{
        try{
            if(stmt !=null){
                stmt.close();
                System.out.println("关闭Statement成功");
            }
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("关闭Statement失败");
        }
    }
    // 关闭ResultSet对象;
    public static void closeResultSet(ResultSet rs) throws Exception{
        try{
            if(rs!=null){
                rs.close();
                System.out.println("关闭ResultSet成功");
            }
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("关闭ResultSet失败");
        }
    }
    //关闭connection对象;
    public static void closeConnection(Connection conn,Statement stm,ResultSet rs)throws Exception{
        try{
            if(rs!= null){
                rs.close();
                System.out.println("关闭rs成功");
            }
            if(stm != null){
                stm.close();
                System.out.println("关闭stm成功");
            }
            if(conn!=null){
                conn.close();
                System.out.println("关闭Connection成功");
            }
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("关闭Connection失败");
        }
    }
    
}

三.创建一个特定的类，来增删改查数据里特定的一张表;

package com.yxq.dao;

import java.sql.Connection;
import java.sql.Date;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.yxq.valuebean.Model_Artical;
import com.yxq.dao.DB;

public class ArticalDao {
    /*
     * @Description: 查询文章;
     * @param :参数是start，end ,分别是数据的第几条数据，和一次查询的数量；
     * @return:返回查询的记录，封装在List中。
     * */
    public List<Model_Artical> query(int start,int end) throws Exception{        
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();
        String sql="SELECT * FROM tbl_artical limit "+start+","+end+"";
        ResultSet rs=  stm.executeQuery(sql);
        List<Model_Artical> model_artical  = new ArrayList<Model_Artical>();
        Model_Artical artical= null;
        while(rs.next()){
            artical = new Model_Artical();
            artical.setArtical_Id(rs.getInt(1));
            artical.setArtical_Name(rs.getString("Artical_Name"));
            artical.setArtical_Content(rs.getString("Artical_Content"));
            artical.setArtical_Date(rs.getDate("Artical_Date"));
            artical.setArtical_Glancenumber(rs.getInt("Artical_Glancenumber"));
            artical.setUser_Id(rs.getInt("User_Id"));
            artical.setArticalTypel_Id(rs.getInt("ArticalTypel_Id"));
            artical.setArtical_Character(rs.getString("Artical_Character"));
            model_artical.add(artical);            
        }
        DB.closeConnection(con,stm,rs);
        return model_artical;
    }
    /*
     * @Description: 查询文章;
     * @param :参数是typeid，start，end ,分别是文章的typeid值和数据的第几条数据，和一次查询的数量；
     * @return:返回查询的记录，封装在List中。
     * */
    public List<Model_Artical> querytype(int typeid,int start,int end) throws Exception{        
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();
        String sql="SELECT * FROM tbl_artical where  ArticalTypel_Id = '"+typeid+"' limit "+start+","+end+"";
        ResultSet rs=  stm.executeQuery(sql);
        List<Model_Artical> model_artical  = new ArrayList<Model_Artical>();
        Model_Artical artical= null;
        while(rs.next()){
            artical = new Model_Artical();
            artical.setArtical_Id(rs.getInt(1));
            artical.setArtical_Name(rs.getString("Artical_Name"));
            artical.setArtical_Content(rs.getString("Artical_Content"));
            artical.setArtical_Date(rs.getDate("Artical_Date"));
            artical.setArtical_Glancenumber(rs.getInt("Artical_Glancenumber"));
            artical.setUser_Id(rs.getInt("User_Id"));
            artical.setArticalTypel_Id(rs.getInt("ArticalTypel_Id"));
            artical.setArtical_Character(rs.getString("Artical_Character"));
            model_artical.add(artical);            
        }
        DB.closeConnection(con,stm,rs);
        return model_artical;
    }
    /*创建用来实现查看文章详细内容的方法---queryArticleSingle()；
     * 该方法带有一个参数。表示文章的id*
     */
    public Model_Artical queryArticleSingle(int id) throws Exception{
        String sql = "select * from tbl_artical where  Artical_Id = '"+id+"'";
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();
        ResultSet rs=  stm.executeQuery(sql);
        try{
            while(rs.next()){
                
                Model_Artical artical = new Model_Artical();
                artical.setArtical_Id(rs.getInt(1));
                artical.setArtical_Name(rs.getString("Artical_Name"));
                artical.setArtical_Content(rs.getString("Artical_Content"));
                artical.setArtical_Date(rs.getDate("Artical_Date"));
                artical.setArtical_Glancenumber(rs.getInt("Artical_Glancenumber"));
                artical.setUser_Id(rs.getInt("User_Id"));
                artical.setArticalTypel_Id(rs.getInt("ArticalTypel_Id"));
                DB.closeConnection(con,stm,rs);
                return artical;
            }
        }catch(Exception e){
            e.printStackTrace();
            System.out.println("按文章类别查看文章失败");
            DB.closeConnection(con,stm,rs);
            return null;
            
        }
        return null;
        
    }
    /* operationArtical()方法 实现对数据库进行其他的更新操作,如添加，修改和删除*/
    public boolean operattionArtical(String oper,Model_Artical artical) throws Exception{
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();        
        String sql = null;
        if(oper.equals("add")){
            sql = "insert into tbl_artical (Artical_Name,Artical_Content,Artical_Date,Artical_Glancenumber,ArticalTypel_Id,User_Id,Artical_Character) values('"+artical.getArtical_Name()+"','"+artical.getArtical_Content()+"','"+new Date(artical.getArtical_Date().getTime())+"','"+artical.getArtical_Glancenumber()+"','"+artical.getArticalTypel_Id()+"','"+artical.getUser_Id()+"','"+artical.getArtical_Character()+"')";
            int rs =  stm.executeUpdate(sql);
            DB.closeConnection(con,stm,null);
            if( rs > 0 ){
                return true;
            }else{
                return false;
            }                
        }        
        return false;
        
    }
    /*创建一个方法是删除相应的文章*/
    public boolean deleteartical(int articalId) throws Exception{
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();
        String sql="delete from tbl_artical where Artical_Id ="+articalId;
        int rs =  stm.executeUpdate(sql);
        if( rs > 0 ){
            DB.closeConnection(con,stm,null);
            System.out.println("删除成功");
            return true;
        }else{
            DB.closeConnection(con,stm,null);
            System.out.println("删除失败");
            return false;
        }
    }
    /*创建一个修改相对应的文章*/
    public boolean modifyarticle(int articleId,String articlecontent,String articlename,String character,int typeid) throws Exception{
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();
        String sql="UPDATE tbl_artical SET Artical_Content ='"+articlecontent+"',Artical_Name='"+articlename+"',Artical_Character ='"+character+"',ArticalTypel_Id="+typeid+" where Artical_Id ="+articleId;
        int rs =  stm.executeUpdate(sql);
        if( rs > 0 ){
            DB.closeConnection(con,stm,null);
            System.out.println("修改成功");
            return true;
        }else{
            DB.closeConnection(con,stm,null);
            System.out.println("修改失败");
            return false;
        }    
    }
    /*
     * @Description: 计算某一类文章或者是全部文章的总数;
     * @param :参数是typeid，判断是某一类文章，还是数据库里的全部文章，
     * @return:返回数量；
     * */
    public int articalnum(int typeid) throws Exception{
        String sql;
        if(typeid > 0){
             sql = "SELECT count(*) FROM tbl_artical where  ArticalTypel_Id = '"+typeid+"'";
        }else{
             sql="SELECT count(*) FROM tbl_artical";
        }
        Connection con = DB.getConnection();
        Statement stm = con.createStatement();
        ResultSet rs=  stm.executeQuery(sql); 
        int i = 0;
        while(rs.next()){
            i = rs.getInt(1);
        }
        DB.closeConnection(con,stm,rs);
        return i;
        
    }
    
}