java数据库操作类

package mengyiju;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class db {
	public Connection conn;
	private String table;
	private String prefix;
	private String where="";
	private String order="";
	private String limit="";
	public db(String table)
	{
		try {
			Properties prop = db.config();
			this.conn=db.getConn();
			this.table=this.checkcase(table);
			this.prefix=prop.get("prefix").toString();
			
		} catch (IOException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
	}
	//构造类
	public static db M(String table)
	{
		return new db(table);
	}
	//添加表前双缀
	public String checkcase(String str){
		char[] head=str.toCharArray();
		char h=head[0];
		if(!Character.isLowerCase(h)){
			return this.prefix+str.toLowerCase();
		}else{
			return str;
		}
	}
	public db where(String where)
	{
		if(this.where=="")
		{
			this.where=" where "+where;
		}else {
			this.where=this.where+" and ("+where+")";
		}
		return this;
	}
	public db limit(int a)
	{
		this.limit=" limit 0,"+String.valueOf(a);
		return this;
	}
	public db limit(int a,int b)
	{
		this.limit=" limit "+String.valueOf(a)+","+String.valueOf(b);
		return this;
	}
	public db order(String order)
	{
		this.order=" ORDER BY "+order;
		return this;
	}
	//查打一个
	public ResultSet select() throws Exception 
	{
		Statement stmt = null;
		stmt = this.conn.createStatement();
		String sql="SELECT * FROM "+this.table+" "+this.where+" "+this.order+" "+this.limit;
		ResultSet rs = stmt.executeQuery(sql);
		this.where="";
		this.order="";
		this.limit="";
		return rs;
	}
	//读取配置
	public static  Properties config() throws IOException
	{
		String root = Thread.currentThread().getContextClassLoader().getResource("../").toString();
		String path =root.substring(root.indexOf("file")+"file".length()+2);
		FileInputStream fis = new FileInputStream(path+"db.properties");
		Properties prop = new Properties();
        prop.load(fis);
        fis.close();
        return prop;
	}
	// JDBC 驱动名及数据库 URL
	public static Connection getConn() throws IOException {
		Connection conn = null;
		try {
			Properties prop = db.config();
			Class.forName(prop.get("jdbc.driver_class").toString());
			conn = DriverManager.getConnection(prop.get("jdbc.connection.url").toString()+"?user="+prop.get("jdbc.connection.username").toString()+"&password="+prop.get("jdbc.connection.password").toString());
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}
}

使用方法如下

try {
			ResultSet abc=db.M("admin_log").order("admin_log_id desc").limit(2,3).select();
			while(abc.next()){
			int id  = abc.getInt("admin_log_id");
            String name = abc.getString("ip");
            String url = abc.getString("is_correct");
            // 输出数据
            out.print("ID: " + id);
            out.print(", ip: " + name);
            out.print(", correct: " + url);
            out.print("\n");
			}
		} catch (Exception e1) {
			// TODO 自动生成的 catch 块
			out.print(e1.getLocalizedMessage());
		}

配置文件在/WEB-INF/db.properties

jdbc.driver_class=com.mysql.jdbc.Driver
jdbc.connection.username=帐号
jdbc.connection.url=jdbc:mysql://localhost/数据库名
jdbc.connection.password=密码
prefix=表前缀