通过反射将查询条件中空条件过滤掉

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;

import java.lang.reflect.Field;

/**
 * Created on 2022/4/26.
 *
 * @author lichuanming
 *
 * 将查询条件中空条件过滤掉
 */
public class CombineQueryWrapperNotNullConditionUnitl {



  public  static <T> QueryWrapper<T> selectByNotNullCondition(T t) {

    Class<? extends T> aClass = (Class<? extends T>) t.getClass();
    QueryWrapper<T> queryWrapper = new QueryWrapper();


    Field[] declaredFields = aClass.getDeclaredFields();
    for (int i = 0; i < declaredFields.length; i++) {
      Field declaredField = declaredFields[i];
      declaredField.setAccessible(true);



      Object o = null;
      try {
        o = declaredField.get(t);
      } catch (IllegalAccessException e) {
        e.printStackTrace();
      }

      if(o==null || "serialVersionUID".equals(declaredField.getName())){
        continue;
      }


      String underLineName = camelToUnderline(declaredField.getName(), 1);
      queryWrapper.eq(underLineName,o);
    }

    return queryWrapper;
  }


  public static final char UNDERLINE = '_';

  //驼峰转下划线
  public static String camelToUnderline(String param, Integer charType) {
    if (param == null || "".equals(param.trim())) {
      return "";
    }
    int len = param.length();
    StringBuilder sb = new StringBuilder(len);
    for (int i = 0; i < len; i++) {
      char c = param.charAt(i);
      if (Character.isUpperCase(c)) {
        sb.append(UNDERLINE);
      }
      if (charType == 2) {
        sb.append(Character.toUpperCase(c));  //统一都转大写
      } else {
        sb.append(Character.toLowerCase(c));  //统一都转小写
      }


    }
    return sb.toString();
  }

  //下划线转驼峰
  public static String underlineToCamel(String param) {
    if (param == null || "".equals(param.trim())) {
      return "";
    }
    int len = param.length();
    StringBuilder sb = new StringBuilder(len);
    Boolean flag = false; // "_" 后转大写标志,默认字符前面没有"_"
    for (int i = 0; i < len; i++) {
      char c = param.charAt(i);
      if (c == UNDERLINE) {
        flag = true;
        continue;   //标志设置为true,跳过
      } else {
        if (flag == true) {
          //表示当前字符前面是"_" ,当前字符转大写
          sb.append(Character.toUpperCase(param.charAt(i)));
          flag = false;  //重置标识
        } else {
          sb.append(Character.toLowerCase(param.charAt(i)));
        }
      }
    }
    return sb.toString();
  }
}