工具类系列---【tk-mybatis查询条件组装类】

tk-mybatis的使用步骤：

1.引入依赖

            <dependency>
                <groupId>tk.mybatisgroupId>
                <artifactId>mapper-spring-boot-starterartifactId>
                <version>2.1.5version>
            dependency>

2.mapper接口继承基础增删改查Mapper，批量增删改查MySqlMapper

public interface StudentMapper extends Mapper<Student>, MySqlMapper<Student> {
}

3.在启动类上加上@MapperScan("com.study.test.mapper.**"),注意导入tkMybatis的包下的注解。

4.查询条件工具类

package com.fast.common.util;

import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import lombok.extern.slf4j.Slf4j;
import tk.mybatis.mapper.entity.Example;

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

/**
 * tk-mybatis条件组装工具类
 * 
 * @author hujw
 * @since 2022/3/9
 */
@Slf4j
public class ExampleUtil {
    
    public static  Example build(T param){
        Example example = new Example(param.getClass());
        example.setOrderByClause("create_time desc");
        return example;
    }

　　//把param中值为空串的字段设置成null，这样tk-mybatis就不会拼接这个条件了
    public static  Example andEqualTo(T param){
        Example example = build(param);
        Example.Criteria criteria = example.createCriteria();
        Class<?> target = param.getClass();
        Field[] fields = target.getDeclaredFields();
        for (Field field : fields) {
            field.setAccessible(true);
            String fieldName = field.getName();
            if (field.getType().equals(String.class)){
                String firstLatter = fieldName.substring(0, 1);
                String upperFieldName = fieldName.replaceFirst(firstLatter, firstLatter.toUpperCase());
                try {
                    Method getMethod = target.getMethod("get" + upperFieldName);
                    String str = (String) getMethod.invoke(param);
                    if (str !=null && StringUtils.isNotBlank(str.trim())){
                        field.set(param,null);
                    }
                } catch (Exception e) {
                    log.warn("ExampleUtil.addEqualTo execute fail,cause:{}",e);
                } 
            }
        }
        
        criteria.andEqualTo(param);
        return example;
    }
}

4.多条件查询示例

Student student = BeanUtil.copyProperties(param,Student.class);
PageHelper.startpage(param.getPageSize(),param.getPageNo());
Example example = ExampleUtil.andEqualTo(param);
List voList = studentMapper.selectByExample(example);
return new PageInfo<>(voList);