动态SQL中if标签：test判断的null和“ “的问题

1.区别

前端传入json

{ "studentName":"程" , "teamName":"" }

后端对应为

Map{ "studentName":"程" , "teamName":"" }

前端传入json

{ "studentName":"程" }

后端对应为

Map{ "studentName":"程" , "teamName":null }

"teamName":""时，test='studentName!=null'为true

"teamName":null时，test='studentName!=null'为false

2.项目源码

//KbsStudentDao//搜索学员（按组名和学员姓名模糊查询，参数可为空）
@Select("<script>"+ "select distinct SYS_USER.USERID as studentID,SYS_USER.USER_NAME as studentName from SYS_USER"+ " LEFT JOIN SYS_USER_ROLE on SYS_USER.USERID=SYS_USER_ROLE.USERID"+ " RIGHT JOIN KBS_TEAM_USER on SYS_USER.USERID=KBS_TEAM_USER.USER_ID"+ " RIGHT JOIN KBS_TEAM on KBS_TEAM.TEAM_ID=KBS_TEAM_USER.TEAM_ID"+ " where ROLEID='ROLE_STUDENT' "+ " <if test='studentName!=null'> and SYS_USER.USER_NAME like '%${studentName}%'</if> "+ " <if test='teamName!=null'> and KBS_TEAM.TEAM_NAME=#{teamName} </if> "+ "</script>")
public ArrayList<KbsStudent> queryStudents(Map<String,Object> map);

//IKbsStudentService//搜索学员（按组名和学员姓名模糊查询，参数可为空）
public QueryResultObject queryStudents(Map<String,Object> map);

//KbsStudentService implements IKbsStudentService@Override
//搜索学员（按组名和学员姓名模糊查询，参数可为空）
public QueryResultObject queryStudents(Map<String,Object> map) {ArrayList<KbsStudent> studentList=kbsStudentDao.queryStudents(map);return RestUtils.wrappQueryResult(studentList);
}

//KbsStudentController@Autowired
private KbsStudentService kbsStudentService;//搜索学员（按组名和学员姓名模糊查询，参数可为空）
@ApiOperation("搜索培训学员（参数可为空）")
@RequestMapping(value="/queryStudents",method=RequestMethod.POST)
public WrappedResult queryStudents(@RequestBody JSONObject json,HttpServletResponse response) {HashMap<String, Object> map=new HashMap<String, Object>();String studentName=json.getString("studentName");String teamName=json.getString("teamName");map.put("studentName", studentName);map.put("teamName",teamName);//********************if(teamName=="" ){map.put("teamName",null);}//********************try{QueryResultObject result=kbsStudentService.queryStudents(map);logger.info("查询成功");return WrappedResult.successWrapedResult(result);}catch(Exception e){logger.error(e.getMessage(),e);String errorMessage="查询异常";if(isDev){errorMessage=e.getMessage();}return WrappedResult.failedWrappedResult("查询异常");}
}

3.运行结果

SQL执行如下

select distinct SYS_USER.USERID as studentID,SYS_USER.USER_NAME as studentName

from SYS_USER LEFT

JOIN SYS_USER_ROLE on SYS_USER.USERID=SYS_USER_ROLE.USERID RIGHT

JOIN KBS_TEAM_USER on SYS_USER.USERID=KBS_TEAM_USER.USER_ID RIGHT

JOIN KBS_TEAM on KBS_TEAM.TEAM_ID=KBS_TEAM_USER.TEAM_ID

WHERE ROLEID='ROLE_STUDENT'

and SYS_USER.USER_NAME like '%程%'