利用java反射机制实现对数据库增加和修改操作泛型类

最新推荐文章于 2021-02-24 08:59:21 发布

原创最新推荐文章于 2021-02-24 08:59:21 发布 · 1.1k 阅读

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CC 4.0 BY-SA版权

文章标签：

#java #数据库 #反射 #泛型

本文介绍了一个使用Java反射技术实现数据库增删改查操作的通用类。该类通过反射机制动态获取JavaBean的属性，从而完成对数据库的操作，提高了代码的复用性和灵活性。

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package cn.com.basedao;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.text.SimpleDateFormat;

import cn.com.db.DButil;
import cn.com.javabean.IsId;

/**
 * @author Kxh
 * @2018.08.02
 * @利用反射实现对数据库增删改查的泛型类
 * javabean 中属性名，类名必须与数据库表中的字段名，表明相同
 */
public class BaseDao<T> {

    /**
     * 对数据库进行插入数据操作
     * @param t1 t1为javabean中的类型
     */
    public void add(T t1) {
        Class c = t1.getClass();
        String Simplename = c.getSimpleName();
        StringBuilder stb = new StringBuilder("insert into  " + Simplename+ " ");
        StringBuilder stbColName = new StringBuilder("(");
        StringBuilder stbValue = new StringBuilder("values(");
        Field[] f = c.getDeclaredFields();
        try {
            int i = f.length - 1;
            for (Field ff : f) {
                String name = ff.getName();
                Class type = ff.getType();
                stbColName.append(name);
                stbValue.append("?");
                if (i > 0) {
                    stbColName.append(",");
                    stbValue.append(",");
                }
                i--;
            }
            stbColName.append(")");
            stbValue.append(")");
            stb.append(stbColName + " " + stbValue);
            Connection conn = DButil.getConn();
            PreparedStatement pstm = null;
            pstm = conn.prepareStatement(new String(stb));
            int result = 0;
            for (i = 0; i < f.length; i++) {
                Object value=null;
                String name  = f[i].getName();
                f[i].setAccessible(true);
                Class type = f[i].getType();
                if (type == String.class) {
                    if (f[i].get(t1) == null) {
                        pstm.setNull(i + 1,Types.VARCHAR);
                    } else {
                        pstm.setObject(i + 1, f[i].get(t1));
                    }
                } else if (type == Date.class) {
                    if (f[i].get(t1) == null) {
                        pstm.setNull(i + 1,Types.DATE);
                    } else {
                        pstm.setObject(i + 1, f[i].get(t1));
                    }
                }else{
                    if (f[i].get(t1) == null) {
                        pstm.setNull(i + 1,Types.INTEGER);
                    } else {
                        pstm.setObject(i + 1, f[i].get(t1));
                    }
                }
            }
            result = pstm.executeUpdate();
            System.out.println(result);

        } catch (SecurityException e) {

            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
/**
 * 对数据库做修改
 * 只需传入一个javabean
 * @param T t1
 * 暂时还没有办法在javabean中标志出主键，所以默认Field[]数组中的一个元素为主键
 */
    public void update(T t1) {
        Class c = t1.getClass();
        String Simplename = c.getSimpleName();
        StringBuilder stb = new StringBuilder("update  " + Simplename + " set ");
        Field[] f = c.getDeclaredFields();
        int i = 0;
        try {
            for (i = 1; i < f.length; i++) {
                String name = f[i].getName();
                Class type = f[i].getType();
                f[i].setAccessible(true);
                System.out.println(name);
                stb.append(name + "=? ");
                if (i + 1 < f.length) {
                    stb.append(",");
                }
            }
            stb.append(" where " + f[0].getName() + " =?");
            System.out.println(stb);
            Connection conn = DButil.getConn();
            PreparedStatement pstm = null;
            pstm = conn.prepareStatement(new String(stb));
            f[0].setAccessible(true);
            pstm.setObject(f.length, f[0].get(t1));
            int result = 0;
            for (i = 1; i < f.length; i++) {
                pstm.setObject(i, f[i].get(t1));
            }
            pstm.setObject(f.length, f[0].get(t1));

            result = pstm.executeUpdate();
            System.out.println(result);

        } catch (SecurityException e) {

            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}
**查询和删除方法会继续更新**