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工单里面可能有0个告警，一个或多个告警，当工单中没有告警的时候也需要将工单显示出来，所以就需要使用工单和告警的做链接查询，下面是具体实例
表：
CREATE TABLE `alarm` ( `id` bigint(20) NOT NULL DEFAULT ‘0‘, `title` varchar(20) DEFAULT NULL, `level` int(11) DEFAULT NULL, `customer_id` bigint(20) DEFAULT NULL, `work_sheet_id` bigint(20) DEFAULT NULL, PRIMARY KEY (`id`), KEY `work_sheet_id` (`work_sheet_id`), CONSTRAINT `alarm_ibfk_1` FOREIGN KEY (`work_sheet_id`) REFERENCES `alarm` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
CREATE TABLE `worksheet` ( `id` bigint(20) NOT NULL DEFAULT ‘0‘, `serialNo` varchar(20) DEFAULT NULL, `seatId` bigint(20) DEFAULT NULL, `device_id` bigint(20) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
insert into alarm values(1,‘title‘,‘1‘,‘1‘,‘1‘); insert into alarm values(2,‘title‘,‘1‘,‘1‘,‘1‘); insert into alarm values(3,‘title‘,‘1‘,‘1‘,‘1‘); insert into alarm values(4,‘title‘,‘1‘,‘1‘,‘1‘); insert into alarm values(5,‘title‘,‘1‘,‘1‘,‘1‘); insert into alarm values(6,‘title‘,‘1‘,‘1‘,‘1‘); insert into worksheet values(1,‘serialno‘,1,1); insert into worksheet values(2,‘serialno‘,1,1); insert into worksheet values(3,‘serialno‘,1,1); insert into worksheet values(4,‘serialno‘,1,1); insert into worksheet values(5,‘serialno‘,1,1); insert into worksheet values(6,‘serialno‘,1,1);
存放SQL文件的接口
package com.h3c.zgc; public interface SQL { public static final String SELECT_WORKSHEET_LEFT_JOIN_ALARM = "select w.serialNo workSheetSerialNo,a.title title,a.level level,a.id alarmId from worksheet w left join alarm a on w.id=a.work_sheet_id where w.id=?"; }
dao层：将连接查询的数据转换成map对象放入list中
package com.h3c.zgc; import java.util.List; import javax.annotation.Resource; import org.hibernate.SQLQuery; import org.hibernate.SessionFactory; import org.hibernate.transform.Transformers; import org.springframework.orm.hibernate4.support.HibernateDaoSupport; import org.springframework.stereotype.Repository; import com.h3c.zgc.alarm.WorkSheet; @Repository public class WorkSheetDao extends HibernateDaoSupport { @Resource private void set(SessionFactory sessionFactory) { this.setSessionFactory(sessionFactory); } public List getWorkSheets(Long worksheetId) { SQLQuery sqlQuery = this .getSessionFactory() .openSession() .createSQLQuery( SQL.SELECT_WORKSHEET_LEFT_JOIN_ALARM); sqlQuery.setParameter(0, worksheetId); sqlQuery.setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP); return sqlQuery.list(); } public WorkSheet getWorkSheet() { SQLQuery sqlQuery = this.getSessionFactory().openSession() .createSQLQuery("select* from worksheet where id=1") .addEntity(WorkSheet.class); List<WorkSheet> list = sqlQuery.list(); return list.get(0); } }
service层：
package com.h3c.zgc; import java.util.Map; import javax.annotation.Resource; import org.springframework.stereotype.Service; @Service public class WorkSheetService { @Resource private WorkSheetDao workSheetDao; public Map<String, Object> getWorkSheet(Long worksheetId){ return (Map<String, Object>) workSheetDao.getWorkSheets(worksheetId).get(0); } }
controller层
package com.h3c.zgc; import java.util.Map; import javax.annotation.Resource; import javax.servlet.http.HttpServletRequest; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; @Controller public class WorkSheetController { @Resource private WorkSheetService workSheetService; @RequestMapping("getArr") public String toGetArr(Long workSheetId,HttpServletRequest request){ Map<String, Object> o = this.workSheetService.getWorkSheet(workSheetId); System.out.println(o.get("alarmId")==null); if(o.get("alarmId")==null){ o.put("alarmId", 0); } request.setAttribute("obj",o); return "test/getWorkSheet"; } }
在页面中获取数据
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> ${obj[‘workSheetSerialNo‘] } ,${obj[‘alarmId‘] },${obj[‘title‘] },${obj[‘level‘] } <c:if test="${obj[‘alarmId‘]==0 }">告警不存在</c:if> </body> </html>
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原文地址：http://www.cnblogs.com/qq931399960/p/4590483.html
