Mybatis-Plus条件构造器select方法返回指定字段

Mybatis-Plus条件构造器select方法返回指定字段

条件构造器select用法

1.返回特定的几个字段 select(字段…)

2.排除某几个字段 select(entiyClass,predicate判断)

3.分组聚合函数 select(“聚合函数”)

搭配service的.listMaps方法,将返回的数据封装到map中

避免了多余字段的返回

实例

实例一：

public AjaxResult listAll(ProjectBuild projectBuild) {
    //只返回了id和name两个字段    
    List> list = this.iProjectBuildService.listMaps(
            Wrappers.lambdaQuery(projectBuild).select(ProjectBuild::getBuildId,ProjectBuild::getBuildName).orderByAsc(ProjectBuild::getBuildId)
    );

    return AjaxResult.success(list);
}
 

示例2

@Test
public void selectByQueryWrapper8(){
    QueryWrapper queryWrapper=new QueryWrapper();
 
    queryWrapper.lambda()
             .select(Employee.class,fieldInfo->!fieldInfo.getColumn().equals("birthday")&&!fieldInfo.getColumn().equals("gender"))
             .gt(Employee::getSalary,3500)
             .like(Employee::getName,"小");
    List employeeList = employeeMapper.selectList(queryWrapper);
    System.out.println(employeeList);
}

示例3

期望的效果是：

SELECT departmentId,AVG(salary) AS avg_salary FROM t_employee GROUP BY department_id;

如下实现

@Test
public void selectByQueryWrapper9(){
    QueryWrapper queryWrapper=new QueryWrapper();
  
    queryWrapper.lambda()
             .select(Employee::getDepartmentId,"AVG(salary) AS avg_salary")
             .groupBy(Employee::getDepartmentId);
    List employeeList = employeeMapper.selectList(queryWrapper);
    System.out.println(employeeList);
}

问题解决

问题描述: map中的key没有使用驼峰命名

解决方法: 使用hutool工具包中的 MapUtil.toCamelCaseMap(map);

//处理map中key未驼峰命名
list = list.stream().map(MapUtil::toCamelCaseMap).collect(Collectors.toList());