关于MybatisPlus 构造器类封装

功能实现：

使用mybatisPlus 根据传入对象（查询条件）根据在对象中加入的注解查询条件 完成对传入对象的查询　　

主要使用方法：

1. mybatisPlus 构造器的使用 2. java反射机制的使用 3.java注解的实现

流程图展示：

1. 构造器实现的主要类：

　　

package com.pig4cloud.pigx.common.data.util;

import cn.hutool.core.util.ReflectUtil;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.pig4cloud.pigx.common.data.annotation.DynamicQuery;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class CreateQuery {

    public static QueryWrapper getQueryWrapper(Object queryObj) {

        int len;
        String fieldName2;
        String first;
        Object endValue;
        Method endMethod;

        Class<?> clazz = queryObj.getClass(); //得到查询类的类
        Field[] fields = clazz.getDeclaredFields();//获取类成员变量
        QueryWrapper queryWrapper = new QueryWrapper();
        for (Field field : fields) {//遍历所有的类成员变量

            DynamicQuery query = field.getAnnotation(DynamicQuery.class); //得到成员变量上的注解
            if (query == null)
                continue;

            Object queryValue = ReflectUtil.getFieldValue(queryObj, field); // 得到注解类的值

            if (queryValue != null) {
                String dbField = query.dbField();
                if (dbField.equals("")) {
                    dbField = CamelUtil.underscoreName(field.getName()); //将驼峰命名法命名为数据库命名法
                }
                switch (query.value()) { //
                    case eq:
                        queryWrapper.eq(dbField, queryValue);
                        break;
                    case ne:
                        queryWrapper.ne(dbField, queryValue);
                        break;
                    case gt:
                        queryWrapper.gt(dbField, queryValue);
                        break;
                    case ge:
                        queryWrapper.ge(dbField, queryValue);
                        break;
                    case lt:
                        queryWrapper.lt(dbField, queryValue);
                        break;
                    case le:
                        queryWrapper.le(dbField, queryValue);
                        break;
                    case like:
                        queryWrapper.like(dbField, queryValue);
                        break;
                    case notLike:
                        queryWrapper.notLike(dbField, queryValue);
                        break;
                    case between:
                        len = field.getName().length();
                        fieldName2 = field.getName().substring(0, len - 2);
                        first = fieldName2.substring(0, 1);
                        fieldName2 = fieldName2.substring(1, len - 2);
                        fieldName2 = first.toUpperCase() + fieldName2 + "End";
                        endMethod = ReflectUtil.getMethod(queryObj.getClass(), fieldName2);
                        try {
                            endValue = endMethod.invoke(queryObj);
                        } catch (Exception e) {
                            e.printStackTrace();
                            continue;
                        }
                        if (endValue != null)
                            queryWrapper.between(dbField, queryValue, endValue);
                        break;

                    case notBetween:
                        len = field.getName().length();
                        fieldName2 = field.getName().substring(0, len - 2);
                        first = fieldName2.substring(0, 1);
                        fieldName2 = fieldName2.substring(1, len - 2);
                        fieldName2 = first.toUpperCase() + fieldName2 + "End";

                        endMethod = ReflectUtil.getMethod(queryObj.getClass(), fieldName2);
                        try {
                            endValue = endMethod.invoke(queryObj);
                        } catch (Exception e) {
                            e.printStackTrace();
                            continue;
                        }
                        if (endValue != null)
                            queryWrapper.notBetween(dbField, queryValue, endValue);
                        break;
                    case likeLeft:
                        queryWrapper.likeLeft(dbField, queryValue);
                        break;
                    case likeRight:
                        queryWrapper.likeRight(dbField, queryValue);
                        break;
                    case isNull:
                        queryWrapper.isNull(dbField);
                        break;
                    case inNotNull:
                        queryWrapper.isNotNull(dbField);
                        break;
                    case in:
                        queryWrapper.in(dbField, queryValue);
                        break;
                    case notIn:
                        queryWrapper.notIn(dbField, queryValue);
                        break;
                    default:
                        break;
                }
            }
        }
        return queryWrapper;
    }
}

2. 通过反射获得成员变量的值类实现：

3. 将驼峰命名字段转换为数据库db字段类实现: