MyBatisPlus条件构造器Condition的用法

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场景

项目搭建专栏：

https://blog.csdn/BADAO_LIUMANG_QIZHI/column/info/37194

基础搭建：

https://blog.csdn/BADAO_LIUMANG_QIZHI/article/details/89407994

条件构造器介绍使用：

https://blog.csdn/BADAO_LIUMANG_QIZHI/article/details/89482201

实现

查看Condition的源码可知其继承自Wrapper方法，所以Wrapper的方法都可以使用。

它有一个获取实例的方法

/**
     * 获取实例
     */
    public static Condition create() {
        return new Condition();
    }

编写测试方法：

/***
  *条件构造器 Condition
  */
 @Test
 public void testConditionOrderBy() {
  
  List<Employee> employeeList=employeeMapper.selectList(Condition.create()
    .eq("gender",1)
    .like("name", "霸")
    .orderBy("age")
    .last("desc limit 1,2")
    //.orderDesc(Arrays.asList(new String[] {"age"}))
    //.orderAsc(Arrays.asList(new String[] {"age"}))
    );
  System.out.println("*******************"+employeeList);
  for (Employee employee : employeeList) {
   System.out.println(employee.getAge());
  }
 }

源码下载

https://download.csdn/download/badao_liumang_qizhi/11142337

Condition源码

/**
 * Copyright (c) 2011-2020, hubin (jobob@qq).
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * <p>
 * http://www.apache/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR EntityWrapperS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.baomidou.mybatisplus.mapper;

import com.baomidou.mybatisplus.toolkit.StringUtils;

/**
 * <p>
 * 条件查询构造器
 * </p>
 *
 * @author hubin Caratacus
 * @date 2016-11-7
 */
@SuppressWarnings({"rawtypes", "serial"})
public class Condition extends Wrapper {

    /**
     * 构建一个Empty条件构造 避免传递参数使用null
     */
    public static final Wrapper EMPTY = new Wrapper() {
        @Override
        public String getSqlSegment() {
            return null;
        }
    };

    /**
     * 获取实例
     */
    public static Condition create() {
        return new Condition();
    }

    /**
     * SQL 片段
     */
    @Override
    public String getSqlSegment() {
        if (SqlHelper.isEmptyOfWrapper(this)) {
            return null;
        }
        /*
         * 无条件
   */
        String sqlWhere = sql.toString();
        if (StringUtils.isEmpty(sqlWhere)) {
            return null;
        }
         /*
         * 根据当前实体判断是否需要将WHERE替换成 AND 增加实体不为空但所有属性为空的情况
   */
        return isWhere != null ? (isWhere ? sqlWhere : sqlWhere.replaceFirst("WHERE", AND_OR)) : sqlWhere.replaceFirst("WHERE", AND_OR);

    }

    /**
     * 构造一个空的Wrapper<T></>
     *
     * @param <T>
     * @return
     */
    public static <T> Wrapper<T> empty() {
        return (Wrapper<T>) EMPTY;
    }

    /**
     * 构造一个Wrapper<T></>
     *
     * @param <T>
     * @return
     */
    public static <T> EntityWrapper<T> wrapper() {
        return new EntityWrapper<>();
    }

}

本文标签： 条件MyBatisPluscondition