SSM學習筆記（一）——多表聯查
阿新 • • 發佈：2019-02-14
在剛剛接觸SSM的時候，最初遇到的難題便是多表聯查的問題。mybatis由於他的特性一般情況下對映的結果與pojo(entity)實體類裡面的屬性都是一一對應的。所以如果是多張表聯合查詢然後返回結果集的話，由於存在pojo裡面的屬性不全的問題無法完成對映，因為這個問題糾結了2天。
找了許多的網站和例子也沒有找到解決的方案，在一次偶然的嘗試中發現瞭解決的方法，因此在這裡做下筆記，作為留念。
需求：從Seorder, Seorderentry, Icitemcore獲取資料顯示到頁面上
要求顯示的資料
Seorder 表的 FBillNo
Seorderentry 表的 FMapNumber，FEntrySelfS0164
Icitemcore 表的 FNumber FShortNumbe FName
首先寫sql語句
SeorderKDao.xml
然後根據xml寫出對應的dao介面，dao中的方法名字與xml中select的id要相同<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="cn.gsp.dao.SeorderKDao"> <sql id="seorderwhere"> <where> <if test="FBillNo!=null and FBillNo!=''"> and t1.FBillNo=#{FBillNo} </if> <if test="FMapNumber!=null and FMapNumber!=''"> and t2.FMapNumber=#{FMapNumber} </if> <if test="FEntrySelfS0164!=null and FEntrySelfS0164!=''"> and t2.FEntrySelfS0164=#{FEntrySelfS0164} </if> </where> </sql> <select id="getByFBillNo" resultType="cn.gsp.pojo.SeorderK" > SELECT t1.FBillNo, t2.FMapNumber, t2.FEntrySelfS0164, t3.FNumber, t3.FShortNumber, t3.FName FROM SEOrder t1 inner join SEOrderEntry t2 on t1.FInterID=t2.FInterID inner join t_ICItemCore t3 on t2.FItemID=t3.FItemID <include refid="seorderwhere"></include> </select> </mapper>
SeorderKDao.java
package cn.gsp.dao;
import java.util.List;
import cn.gsp.pojo.SeorderK;
public interface SeorderKDao {
/**
* 通過查詢條件來查詢資料
*/
public List<SeorderK> getByFBillNo()throws Exception;
}
之後是重點，實體類
這裡要寫4個實體類，3個是資料庫中對應的表的實體類，第四個則是對映結果集的實體類，這點非常重要。
1.Seorder.java
package cn.gsp.pojo;
public class Seorder {
private String FBillNo;
private int FInterID;
private Seorderentry seorderentry;
private Icitemcore icitemcore;
public Icitemcore getIcitemcore() {
return icitemcore;
}
public void setIcitemcore(Icitemcore icitemcore) {
this.icitemcore = icitemcore;
}
public Seorderentry getSeorderentry() {
return seorderentry;
}
public void setSeorderentry(Seorderentry seorderentry) {
this.seorderentry = seorderentry;
}
public String getFBillNo() {
return FBillNo;
}
public void setFBillNo(String fBillNo) {
FBillNo = fBillNo;
}
public int getFInterID() {
return FInterID;
}
public void setFInterID(int fInterID) {
FInterID = fInterID;
}
@Override
public String toString() {
return "Seorder [FBillNo=" + FBillNo + ", FInterID=" + FInterID + ", seorderentry=" + seorderentry + "]";
}
}2.Seorderentry.java
package cn.gsp.pojo;
public class Seorderentry {
private String FMapNumber;
private String FEntrySelfS0164;
private int FInterID;
private int FItemID;
private Icitemcore icitemcore;
private Seorder seorder;
public Seorder getSeorder() {
return seorder;
}
public void setSeorder(Seorder seorder) {
this.seorder = seorder;
}
public Icitemcore getIcitemcore() {
return icitemcore;
}
public void setIcitemcore(Icitemcore icitemcore) {
this.icitemcore = icitemcore;
}
public String getFMapNumber() {
return FMapNumber;
}
public void setFMapNumber(String fMapNumber) {
FMapNumber = fMapNumber;
}
public String getFEntrySelfS0164() {
return FEntrySelfS0164;
}
public void setFEntrySelfS0164(String fNewNo) {
FEntrySelfS0164 = fNewNo;
}
public int getFInterID() {
return FInterID;
}
public void setFInterID(int fInterID) {
FInterID = fInterID;
}
public int getFItemID() {
return FItemID;
}
public void setFItemID(int fItemID) {
FItemID = fItemID;
}
@Override
public String toString() {
return "Seorderentry [FMapNumber=" + FMapNumber + ", FEntrySelfS0164=" + FEntrySelfS0164 + ", FInterID="
+ FInterID + ", FItemID=" + FItemID + ", icitemcore=" + icitemcore + "]";
}
}
3.Icitemcore.java
package cn.gsp.pojo;
public class Icitemcore {
private String FNumber;
private String FShortNumber;
private String FName;
private int FItemID;
private Seorderentry seorderentry;
private Seorder seorder;
public Seorder getSeorder() {
return seorder;
}
public void setSeorder(Seorder seorder) {
this.seorder = seorder;
}
public Seorderentry getSeorderentry() {
return seorderentry;
}
public void setSeorderentry(Seorderentry seorderentry) {
this.seorderentry = seorderentry;
}
public String getFNumber() {
return FNumber;
}
public void setFNumber(String fNumber) {
FNumber = fNumber;
}
public String getFShortNumber() {
return FShortNumber;
}
public void setFShortNumber(String fShortNumber) {
FShortNumber = fShortNumber;
}
public String getFName() {
return FName;
}
public void setFName(String fName) {
FName = fName;
}
public int getFItemID() {
return FItemID;
}
public void setFItemID(int fItemID) {
FItemID = fItemID;
}
@Override
public String toString() {
return "Icitemcore [FNumber=" + FNumber + ", FShortNumber=" + FShortNumber + ", FName=" + FName
+ ", FItemID=" + FItemID + "]";
}
}
package cn.gsp.pojo;
public class SeorderK extends Seorder{
private String FMapNumber;
private String FEntrySelfS0164;
private String FNumber;
private String FShortNumber;
private String FName;
public String getFMapNumber() {
return FMapNumber;
}
public void setFMapNumber(String fMapNumber) {
FMapNumber = fMapNumber;
}
public String getFEntrySelfS0164() {
return FEntrySelfS0164;
}
public void setFEntrySelfS0164(String fEntrySelfS0164) {
FEntrySelfS0164 = fEntrySelfS0164;
}
public String getFNumber() {
return FNumber;
}
public void setFNumber(String fNumber) {
FNumber = fNumber;
}
public String getFShortNumber() {
return FShortNumber;
}
public void setFShortNumber(String fShortNumber) {
FShortNumber = fShortNumber;
}
public String getFName() {
return FName;
}
public void setFName(String fName) {
FName = fName;
}
}寫完實體類後，開始業務層程式碼，這裡只是簡單的寫一個顯示列表的程式碼
SeorderService.java Service的介面
package cn.gsp.service;
import java.util.List;
import cn.gsp.pojo.SeorderK;
public interface SeorderService {
List<SeorderK> getByFBillNo() throws Exception;
}
接著寫介面對應的實現方法
SeoderServiceImpl.java
package cn.gsp.service;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import cn.gsp.dao.SeorderKDao;
import cn.gsp.pojo.SeorderK;
@Service
@Transactional(readOnly = true)
public class SeoderServiceImpl implements SeorderService{
@Autowired
private SeorderKDao seorderkDao;
@Override
public List<SeorderK> getByFBillNo() throws Exception {
List<SeorderK> list=seorderkDao.getByFBillNo();
return list;
}
}
接下來是controller層
package cn.gsp.controller;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import cn.gsp.pojo.SeorderK;
import cn.gsp.service.SeorderService;
@Controller
@RequestMapping("/seorder")
public class SeorderController {
@Autowired
private SeorderService seorderService;
@RequestMapping("/list")
public String list(Model model) throws Exception{
//查詢資料列表和資料總數
List<SeorderK> resutList = seorderService.getByFBillNo();
model.addAttribute("resutList", resutList);
return "seorder";
}
}
根據最後的return"seorder" 再寫一個返回的頁面就可以了
seorder.jsp 的主要部分
<div class="resutList">
<div class="col-lg-12">
<div class="panel panel-default">
<div class="panel-heading">資訊列表</div>
<!-- /.panel-heading -->
<table class="table table-bordered table-striped">
<thead>
<tr>
<th>訂單編號</th>
<th>客戶程式碼</th>
<th>新編碼</th>
<th>GSP長程式碼</th>
<th>GSP短程式碼</th>
<th>GSP名稱</th>
</tr>
</thead>
<tbody>
<c:forEach items="${resutList}" var="resutList">
<tr>
<td>${resutList.FBillNo}</td>
<td>${resutList.FMapNumber}</td>
<td>${resutList.FEntrySelfS0164}</td>
<td>${resutList.FNumber}</td>
<td>${resutList.FShortNumber}</td>
<td>${resutList.FName}</td>
</tr>
</c:forEach>
</tbody>
</table>
</div>
</div>
</div>
</div>以上的內容全為初學者的一己之見，如有問題和錯誤，感謝提出寶貴的建議，謝謝！！！