java手写的一些常用的工具类（DButils，日期工具类，MD5加密工具类）

2021-06-24 13:58 354阅读 0赞

### java常用的一些工具类 ###

*   *  日期工具类
     *  MD5加密工具类
     *  DBUtils工具类
     *  对事务封装的DButis
     *  DaoUtils
     *   *  RowMapper 接口
         *  PersonRowMapper 实现类
     *  Druid DButils
     *  生成验证码

## 日期工具类 ##

Date工具类封装

package Dao;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    public class Dateutils { 
    
        public  static final SimpleDateFormat sdf=new SimpleDateFormat("yy-MM-dd");
    
        public static java.util.Date strtoutildate(String str){ 
    
            try { 
                Date date = sdf.parse(str);
                return date;
            } catch (ParseException e) { 
                e.printStackTrace();
            }
            return null;
        }
        
    
        public static  java.sql.Date utiltosqldate(java.util.Date date){ 
    
            return new java.sql.Date(date.getTime());
        }
    
    
        public static String utildatetostr(java.util.Date date){ 
    
             String format = sdf.format(date);
    
              return format;
        }
    }

## MD5加密工具类 ##

import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;
    
    public class MD5utils { 
        /** * 密码加密 */
        public static  String encrypt(String password) throws NoSuchAlgorithmException { 
            //获得MD5加密对象
            MessageDigest md5=MessageDigest.getInstance("md5");
            //对原密码加密
            md5.update(password.getBytes());
            //获得加密后的密码字节
            byte[] digest = md5.digest();
            //将字节转化为密码字符串
            StringBuilder builder = new StringBuilder();
            for(byte b: digest)
            { 
                //转化为16进制字符串
                //将高4位转换为16进制
                builder.append(Integer.toHexString(b>>4&0xf));
                //将低4位转换为16进制
                builder.append(Integer.toHexString(b&0xf));
            }
            return builder.toString();
    
    
        }
    
    }

import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;
    
    public class MD5Util { 
    	
    	public static String getMD5(String password) { 
    		try { 
    			// 得到一个信息摘要器
    			MessageDigest digest = MessageDigest.getInstance("md5");
    			byte[] result = digest.digest(password.getBytes());
    			StringBuffer buffer = new StringBuffer();
    			// 把每一个byte 做一个与运算 0xff;
    			for (byte b : result) { 
    				// 与运算
    				int number = b & 0xff;// 加盐
    				String str = Integer.toHexString(number);
    				if (str.length() == 1) { 
    					buffer.append("0");
    				}
    				buffer.append(str);
    			}
    
    			// 标准的md5加密后的结果
    			return buffer.toString();
    		} catch (NoSuchAlgorithmException e) { 
    			e.printStackTrace();
    			return "";
    		}
    	}
    	
    }

## DBUtils工具类 ##

package com.blb.utils;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    public class DBUtils { 
    
    	private static Connection conn = null;
    	
    	static{ 
    		try { 
    			Class.forName("com.mysql.jdbc.Driver");
    			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/sys?useUnicode=true&characterEncoding=UTF-8", "root", "root");
    		} catch (ClassNotFoundException | SQLException e) { 
    			e.printStackTrace();
    		}
    	}
    	
    	/** * 执行查询 * @param sql * @param params * @return * @throws SQLException */
    	public static ResultSet executeQuery(String sql, String... params) throws SQLException{ 
    		return getParams(sql, params).executeQuery();
    	}
    	
    	/** * 执行添加、删除、修改 * @param sql * @param params * @throws SQLException */
    	public static void execute(String sql, String... params) throws SQLException{ 
    		getParams(sql, params).executeUpdate();
    	}
    	
    	/** * 参数处理 * @param sql * @param params * @return * @throws SQLException */
    	private static PreparedStatement getParams(String sql, String... params) throws SQLException{ 
    		PreparedStatement prepareStatement = conn.prepareStatement(sql);
    		for (int i = 0; i < params.length; i++) { 
    			prepareStatement.setObject(i+1, params[i]);
    		}
    		return prepareStatement;
    	}
    }

## 对事务封装的DButis ##

package account;
    
    
    import JDBC.DBUtils;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.sql.*;
    import java.util.Properties;
    
    public class DButils { 
         private static final Properties PROPERTIES=new Properties();
         private static  final  ThreadLocal<Connection> THREAD_LOCAL=new ThreadLocal<>();
         static { 
             InputStream is = DBUtils.class.getResourceAsStream("/db.properties");
             try { 
                 PROPERTIES.load(is);
                 Class.forName(PROPERTIES.getProperty("driver"));
             } catch (IOException | ClassNotFoundException e) { 
                 e.printStackTrace();
             }
    
         }
    
         public  static Connection getconnection(){ 
               Connection conn=THREAD_LOCAL.get();//获取线程中存储的connection对象
    
             try { 
                 if(conn==null){ //如果连接对象为空则创建连接
                     conn= DriverManager.getConnection(PROPERTIES.getProperty("url"),PROPERTIES.getProperty("username"),PROPERTIES.getProperty("password"));
                     THREAD_LOCAL.set(conn);//把连接存在当前线程共享中
                 }
    
                return conn;
             } catch (SQLException throwables) { 
                 throwables.printStackTrace();
             }
             return  null;
         }
        //事务的开启
         public static void begin()
         { 
            Connection conn=null;
            try { 
                conn=getconnection();
                conn.setAutoCommit(false);
            }catch (SQLException e)
            { 
                e.printStackTrace();
            }
    
         }
         //提交事务
          public static void commit()
          { 
              Connection conn=null;
              try { 
                  conn=getconnection();
                  conn.commit();
              }catch (SQLException e)
              { 
                  e.printStackTrace();
              }finally { 
                  DBUtils.closeall(conn,null,null);
              }
          }
          //回滚事务
          public static void rollback()
          { 
              Connection conn=null;
              try { 
                  conn=getconnection();
                  conn.rollback();
              }catch (SQLException e)
              { 
                  e.printStackTrace();
              }finally { 
                  DBUtils.closeall(conn,null,null);
              }
    
          }
        public static void closeall(Connection conn, PreparedStatement pst, ResultSet rs){ 
            if(rs!=null){ 
                try { 
                    rs.close();
                } catch (SQLException throwables) { 
                    throwables.printStackTrace();
                }
            }
    
            if(pst!=null){ 
                try { 
                    pst.close();
                } catch (SQLException throwables) { 
                    throwables.printStackTrace();
                }
            }
    
            if(conn!=null){ 
                try { 
                    conn.close();
                    THREAD_LOCAL.remove();//关闭连接后移除已关闭的connection对象
                } catch (SQLException throwables) { 
                    throwables.printStackTrace();
                }
            }
    
        }
    }

## DaoUtils ##

package com.blb.utils;
    
    import com.blb.advanced.RowMapper;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.List;
    
    
    public class Daoutils<T>{ 
        /** * 公共处理增删改的方法 * @param sql 执行的sql语句 * @param args 参数列表 * @return */
        public  int commonsUpdate(String sql,Object...args){ 
            Connection conn=null;
            PreparedStatement pst=null;
             conn = DButils.getConnection();
            try { 
                pst=conn.prepareStatement(sql);
                for(int i=0;i<args.length;i++){ 
                    pst.setObject(i+1,args[i]);
                }
                 int i = pst.executeUpdate();
                 return i;
            } catch (SQLException e) { 
                e.printStackTrace();
            }finally { 
                DButils.closeall(null,pst,null);
            }
    
            return 0;
        }
    
        public  List<T> commonsSelect(String sql, RowMapper<T> rowMapper,Object...args)
        { 
            List<T> arr=new ArrayList<>();
            Connection conn=null;
            PreparedStatement pst=null;
            ResultSet rs=null;
    
            try { 
                conn=DButils.getConnection();
                pst=conn.prepareStatement(sql);
    
                 if(args!=null){ //注意要判断非空否则查询所有的时候会报错误
    
                     for(int i=0;i<args.length;i++)
                     { 
                         pst.setObject(i+1,args[i]);
                     }
                 }
                rs = pst.executeQuery();
                 while (rs.next()){ 
                     //根据查询到的结果完成orm
                     T t=rowMapper.getRow(rs);
                     arr.add(t);
    
                 }
                 return arr;
            } catch (SQLException e) { 
                e.printStackTrace();
            }finally { 
                DButils.closeall(null,pst,rs);
            }
    
            return null;
        }
    }

在建一个包用于实现查询里面的orm映射，并且使用泛型这样可以供所有的使用

### RowMapper 接口 ###

package com.blb.advanced;
    
    import java.sql.ResultSet;
    
    public interface RowMapper<T> { 
        public T getRow(ResultSet rs);
    }

### PersonRowMapper 实现类 ###

package com.blb.advanced.Impl;
    
    import com.blb.advanced.RowMapper;
    import com.blb.entity.Person;
    
    import java.sql.Date;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    public class PersonRowMapper implements RowMapper<Person> { 
        @Override
        public Person getRow(ResultSet rs) { 
            Person person=null;
            int id1 = 0;
            try { 
                id1 = rs.getInt("id");
                int age = rs.getInt("age");
                String name = rs.getString("name");
                String email = rs.getString("email");
                String address = rs.getString("address");
                Date date = rs.getDate("borndate");
                person=new Person(id1,name,age,date,email,address);
    
                return person;
            } catch (SQLException e) { 
                e.printStackTrace();
            }
    
            return null;
        }
    }

## Druid DButils ##

package com.blb.utils;
    
    import com.alibaba.druid.pool.DruidDataSource;
    import com.alibaba.druid.pool.DruidDataSourceFactory;
    
    import javax.sql.DataSource;
    import java.io.IOException;
    import java.io.InputStream;
    import java.sql.*;
    import java.util.Properties;
    
    public class DButils { 
        //声明连接池对象
        private static DruidDataSource ds;
        private  static  final  ThreadLocal<Connection> THREAD_LOCAL=new ThreadLocal<>();
        static { 
            //实例化配置对象
            Properties properties=new Properties();
             InputStream inputStream= DButils.class.getResourceAsStream("/db.properties");
            try { 
                properties.load(inputStream);
                ds=(DruidDataSource) DruidDataSourceFactory.createDataSource(properties);
            } catch (IOException e) { 
                e.printStackTrace();
            } catch (Exception e) { 
                e.printStackTrace();
            }
        }
    
        //获取连接对象
        public static Connection getConnection()
        { 
            Connection conn=THREAD_LOCAL.get();
            try { 
                if(conn == null){ 
                    conn=ds.getConnection();
                    THREAD_LOCAL.set(conn);
                }
    
            } catch (SQLException e) { 
                e.printStackTrace();
            }
            return null;
        }
        public static void begin(){ 
            Connection conn=null;
    
            try { 
                conn=getConnection();
                conn.setAutoCommit(false);
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        public static void commit(){ 
            Connection conn=null;
    
            try { 
                conn=getConnection();
                conn.commit();
            } catch (SQLException e) { 
                e.printStackTrace();
            }finally { 
                closall(conn,null,null);
            }
        }
    
        public static  void rollback()
        { 
            Connection conn=null;
    
            try { 
                conn=getConnection();
                conn.rollback();
            } catch (SQLException e) { 
                e.printStackTrace();
            }finally { 
                closall(conn,null,null);
            }
    
        }
        public static void closall(Connection conn, PreparedStatement pst, ResultSet rs){ 
    
                try { 
                    if(rs!=null){ 
                    rs.close();
                    if(pst!=null){ 
                        pst.close();
                    }
                    if(conn!=null){ 
                        conn.close();
                        THREAD_LOCAL.remove();
                    }
                }
            } catch (SQLException e) { 
                    e.printStackTrace();
                }
    
        }
        //返回一个数据源
        public static DataSource getDataSource(){ 
                return ds;
        }
    }

## 生成验证码 ##

需要 ValidateCode.jar包  
**页面**

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
      <head>
        <title>登录</title>
      </head>
      <body>
       <form action="login" method="post">
         用户名:<input type="text" name="username" /><br>
         密码:<input type="password" name="password" /><br>
         验证码:<input type="text" name="vcode" /><img src="/servlet01_war_exploded/createcode"><br>
           <input type="submit" value="登录">
       </form>
      </body>
    </html>

**生成验证码**

package com.blb.demo;
    
    import cn.dsna.util.images.ValidateCode;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    @WebServlet("/createcode")
    public class CreateCode extends HttpServlet { 
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
             doGet(request,response);
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
            ValidateCode vc=new ValidateCode(100,50,4,10);
            //获得生成验证码里的内容
            String code = vc.getCode();
             HttpSession session = request.getSession();
             session.setAttribute("code",code);
             //响应给客户端
            vc.write(response.getOutputStream());
        }
    }

生成ValidateCode对象的四个参数分别是：宽，高，字符个数，划线的个数