本文共 4986 字，大约阅读时间需要 16 分钟。

Java_反射_SQL增删改查

#Java Bean

package com.hp.beans;/** * Java类 User */public class user {private Integer uid;private String uname;private String upass;private String isadmin;    public Integer getUid() {        return uid;    }    public void setUid(Integer uid) {        this.uid = uid;    }    public String getUname() {        return uname;    }    public void setUname(String uname) {        this.uname = uname;    }    public String getUpass() {        return upass;    }    public void setUpass(String upass) {        this.upass = upass;    }    public String getIsadmin() {        return isadmin;    }    public void setIsadmin(String isadmin) {        this.isadmin = isadmin;    }    @Override    public String toString() {        return "user{" +                "uid=" + uid +                ", uname='" + uname + '\'' +                ", upass='" + upass + '\'' +                ", isadmin='" + isadmin + '\'' +                '}';    }    public user(Integer uid, String uname, String upass, String isadmin) {        this.uid = uid;        this.uname = uname;        this.upass = upass;        this.isadmin = isadmin;    }    public user() {    }}

#获得链接

package com.hp.reflect;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;/** * 获取Sql连接的类 */public class GetConnection{    /**     * 获取sql的连接对象     * @return     */    public Connection getCon(){        //定义连接对象        Connection conn=null;        try {            //加载MySql数据库驱动            Class.forName("com.mysql.jdbc.Driver");            //通过DriverManager.getConnection(url,username,password)获取数据库的连接            conn= DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");        } catch (ClassNotFoundException | SQLException e) {            e.printStackTrace();        }        //将获取的数据库连接返回        return conn;    }}

#增删改查

package com.hp.reflect;import com.hp.beans.user;import java.lang.reflect.Field;import java.sql.*;import java.util.ArrayList;import java.util.List;/** * 反射_sql查询 */public class DaoImpl {    //定义接收的类型为泛型集合    public 
    
      List
     
       select(T t) throws SQLException, IllegalAccessException, InstantiationException {        //Class.getSimpleName()通过泛型获取对象名        String sql="select * from "+t.getClass().getSimpleName();        //实例化List泛型        List
      
        li=new ArrayList
       
        ();        //实例化GetConnection类，通过getCon方法获取Sql的连接        Connection con = new GetConnection().getCon();        //通过连接的prepareStatement()的方法执行sql语句        //调用executeQuery()执行查询获取查询的结果集合        ResultSet res = con.prepareStatement(sql).executeQuery();        //通过resultSet.getMetadata()将结果集合转换为ResultMetaData对象        ResultSetMetaData md = res.getMetaData();        //获取结果的列数        int count = md.getColumnCount();        //获取java对象的属性数组        Field[] filds = t.getClass().getDeclaredFields();        //调用next方法遍历结果集合        while(res.next()) {            //将泛型类实例化为对象            T t2 = (T) t.getClass().newInstance();            //循环泛型对象的属性值            for (int i = 0; i < filds.length; i++) {                //输出当前的属性                System.out.println(filds[i]);                //循环遍历当前结果集中的对象的属性                for (int k = 0; k < count; k++) {                    //获取此条信息的列的名字                    String columnName = md.getColumnName(k + 1);                    //判断结果集中的列名与Java类中的属性名是否对应                    if (filds[i].getName().toUpperCase().equals(columnName.toUpperCase())) {                        //修改类的Accessible为true，使当前属性可以修改                        filds[i].setAccessible(true);                        //res.getObject(列名) 获取当前这条信息的列名的数据                        //调用Filed类的set方法，给当前对象赋值                        filds[i].set(t2, res.getObject(columnName));                    }                }            }            //将循环赋值完成的类添加到集合中            li.add(t2);        }        //返回结果        return li;    }    /**     * 更新     * @param t     * @param 
        
              * @return     */    public 
         
           T update(T t){ try { Field[] filds = t.getClass().getDeclaredFields(); filds[0].setAccessible(true); String tiao=""; for(int i=1;i
          
            * @return * @throws IllegalAccessException */ public 
           
             T insert(T t) throws IllegalAccessException { Field[] filds = t.getClass().getDeclaredFields(); String columnName=""; String columnValue=""; for (int i=0;i
            
             0){ System.out.println("Successful!"); } else{ System.out.println("Error!"); } } catch (SQLException e) { e.printStackTrace(); } return null; } /** * 反射删除 * @param t * @param 
             
               * @return */ public 
              
                T delete(T t) throws SQLException { Field fild = t.getClass().getDeclaredFields()[0]; fild.setAccessible(true); try { String sql="delete from "+t.getClass().getSimpleName()+" where "+fild.getName()+" = "+fild.get(t); System.out.println(sql); int i=new GetConnection().getCon().prepareStatement(sql).executeUpdate(); if(i>0){ System.out.println("Successful!"); } else{ System.out.println("Error!"); } } catch (IllegalAccessException e) { e.printStackTrace(); } return null; }}