Mybatis分頁外掛PageHelper的學習與使用
目錄
- 中文教程
- PageHelper使用
後端程式設計師都知道,在Web系統中,分頁是一種常見的功能,我之前寫的分頁方法都比較麻煩,移植性也不高,這就很不樂觀了。作為一個積極開朗的程式設計師,怎麼能不去了解PageHelper分頁外掛呢?PageHelper是國內非常優秀的一款開源的mybatis分頁外掛,它支援基本主流與常用的資料庫,一致支援mysql、oracle、mariaDB、DB2、SQLite、Hsqldb等。OK接下來就一起來了解了解PageHelper分頁外掛!
@
中文教程
首先,推薦兩個PageHelper分頁外掛專案地址,這裡面有中文教程:
github 專案
gitosc 專案
PageHelper使用
至於怎麼使用我想上面提供的兩個專案講的絕逼講的比我清楚,下面直接進入PageHelper使用實戰
首先,整合引入分頁外掛有下面2種方式,一種是直接下jar包一種是mawen依賴,推薦使用 Maven 方式。
方法一: 直接下載jar包
jar包下載地址,由於使用了sql 解析工具,你還需要下載 jsqlparser.jar
方法二: Maven新增依賴
<dependency> <groupId>com.github.pagehelper</groupId> <artifactId>pagehelper</artifactId> <version>5.1.2</version> </dependency>
1.匯入maven依賴分頁外掛
我這裡就採用方法二maven依賴
2.各個情況下xml的配置
情況一
:如果是mybatis單獨使用PageHelper分頁外掛的時候,就需要在xml配置中新增如下程式碼:
<!-- plugins在配置檔案中的位置必須符合要求,否則會報錯,順序如下properties?, settings?, typeAliases?, typeHandlers?, objectFactory?,objectWrapperFactory?, plugins?, environments?, databaseIdProvider?, mappers? --> <!-- com.github.pagehelper為PageHelper類所在包名 --> <plugins> <!-- 使用下面的方式配置引數,推薦的兩個專案中有所有的引數介紹 --> <plugin interceptor="com.github.pagehelper.PageInterceptor"> <property name="param1" value="value1"/> </plugin> </plugins>
情況二
:顯然,我是這個是ssm專案,mybatis是交由spring的IOC容器管理的,就需要在spring的xml配置中新增如下程式碼(建立工廠中新增):
<!-- 把交給IOC管理 SqlSessionFactory -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<!-- 傳入PageHelper的外掛 -->
<property name="plugins">
<array>
<!-- 傳入外掛的物件 -->
<bean class="com.github.pagehelper.PageInterceptor">
<property name="properties">
<props>
<prop key="helperDialect">oracle</prop>
<prop key="reasonable">true</prop>
</props>
</property>
</bean>
</array>
</property>
</bean>
下面用一個圖來分析一下兩個引數作用:
更多情況請參考上面推薦的專案~
3.Controller程式碼編寫
上面我們配置完了,至於為什麼從controller程式碼開始是因為controller呼叫service嘛,這樣編寫程式碼更方便快捷!為了看出差別,未分頁的controller程式碼方法如下:
@Controller
@RequestMapping("/orders")
public class OrdersController {
@Autowired
private IOrdersService ordersService;
//查詢所有orders未分頁
@RequestMapping("/findAll.do")
public ModelAndView findAll() {
ModelAndView mv = new ModelAndView();
List<Orders> ordersList = ordersService.findAll();
mv.addObject("ordersList", ordersList);
mv.setViewName("orders-list");
return mv;
}
}
而採用了分頁程式碼則是如下:
//採用分頁程式碼方法
@RequestMapping("/findAll.do")
public ModelAndView findAll(@RequestParam(name="page",required = true,defaultValue = "1")int page,@RequestParam(name="size",required = true,defaultValue = "4")int size ) {
ModelAndView mv = new ModelAndView();
List<Orders> ordersList = ordersService.findAll(page,size);
//PageInfo就是一個分頁Bean
PageInfo pageInfo =new PageInfo(ordersList);
mv.addObject("pageInfo", pageInfo);
mv.setViewName("orders-list");
return mv;
}
可以發現多了兩個引數分別是page
和size
4.Service介面程式碼編寫
public interface IOrdersService {
List<Orders> findAll(int page,int size);
}
5.Service實現類程式碼編寫
在執行sql之前(ServiceImpl),使用PageHelper分頁,引數pageNum
是頁碼值 引數pageSize
代表是每頁顯示條數。在ServiceImpl中,使用PageHelper分頁操作程式碼如下:
@Service
public class OrdersServiceImpl implements IOrdersService {
@Autowired
private IOrdersDao ordersDao;
@Override
public List<Orders> findAll(int page,int size) {
//引數pageNum 是頁碼值 引數pageSize 代表是每頁顯示條數
PageHelper.startPage(page, size);
return ordersDao.findAll();
}
}
特別注意:在編寫PageHelper分頁程式碼時的 PageHelper.startPage(page, size)
這一句必須寫在查詢方法的上一句,中間不能新增任何程式碼,否則失效!
6.jsp頁面未處理程式碼
沒有更改的jsp頁面程式碼,普通查詢關鍵更改程式碼塊,注意這裡接收資料為 ordersList
<c:forEach items="${ordersList}" var="orders">
<tr>
<td><input name="ids" type="checkbox"></td>
...
<td>...</td>
</td>
</tr>
</c:forEach>
這下面的程式碼則是未分頁邏輯程式碼
<div class="box-tools pull-right">
<ul class="pagination">
<li>
<a href="#" aria-label="Previous">首頁</a>
</li>
<li><a href="#">上一頁</a></li>
<li><a href="#">1</a></li>
<li><a href="#">2</a></li>
<li><a href="#">3</a></li>
<li><a href="#">4</a></li>
<li><a href="#">5</a></li>
<li><a href="#">下一頁</a></li>
<li>
<a href="#" aria-label="Next">尾頁</a>
</li>
</ul>
</div>
</div>
7.jsp頁面處理後代碼
更改後的jsp頁面程式碼,分頁查詢的關鍵更改程式碼塊,注意這裡接收資料為 ordersList.list
<c:forEach items="${ordersList.list}" var="orders">
<tr>
<td><input name="ids" type="checkbox"></td>
...
<td>...</td>
</td>
</tr>
</c:forEach>
這下面的程式碼則是分頁邏輯程式碼
<div class="box-tools pull-right">
<ul class="pagination">
<li>
<a href="${pageContext.request.contextPath}/orders/findAll.do?page=1&size=${pageInfo.pageSize}" aria-label="Previous">首頁</a>
</li>
<li><a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageInfo.pageNum-1}&size=${pageInfo.pageSize}">上一頁</a></li>
<c:forEach begin="1" end="${pageInfo.pages}" var="pageNum">
<li><a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageNum}&size=${pageInfo.pageSize}">${pageNum}</a></li>
</c:forEach>
<li><a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageInfo.pageNum+1}&size=${pageInfo.pageSize}">下一頁</a></li>
<li>
<a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageInfo.pages}&size=${pageInfo.pageSize}" aria-label="Next">尾頁</a>
</li>
</ul>
</div>
</div>
8.jsp頁面處理前後程式碼分析
//PageInfo就是一個分頁Bean
PageInfo pageInfo =new PageInfo(ordersList);
為了能看到上面的pageInfo原始碼,我就把程式碼貼在下面了
package com.github.pagehelper;
import java.io.Serializable;
import java.util.Collection;
import java.util.List;
public class PageInfo<T> implements Serializable {
private static final long serialVersionUID = 1L;
private int pageNum;
private int pageSize;
private int size;
private int startRow;
private int endRow;
private long total;
private int pages;
private List<T> list;
private int prePage;
private int nextPage;
private boolean isFirstPage;
private boolean isLastPage;
private boolean hasPreviousPage;
private boolean hasNextPage;
private int navigatePages;
private int[] navigatepageNums;
private int navigateFirstPage;
private int navigateLastPage;
public PageInfo() {
this.isFirstPage = false;
this.isLastPage = false;
this.hasPreviousPage = false;
this.hasNextPage = false;
}
public PageInfo(List<T> list) {
this(list, 8);
}
public PageInfo(List<T> list, int navigatePages) {
this.isFirstPage = false;
this.isLastPage = false;
this.hasPreviousPage = false;
this.hasNextPage = false;
if (list instanceof Page) {
Page page = (Page)list;
this.pageNum = page.getPageNum();
this.pageSize = page.getPageSize();
this.pages = page.getPages();
this.list = page;
this.size = page.size();
this.total = page.getTotal();
if (this.size == 0) {
this.startRow = 0;
this.endRow = 0;
} else {
this.startRow = page.getStartRow() + 1;
this.endRow = this.startRow - 1 + this.size;
}
} else if (list instanceof Collection) {
this.pageNum = 1;
this.pageSize = list.size();
this.pages = this.pageSize > 0 ? 1 : 0;
this.list = list;
this.size = list.size();
this.total = (long)list.size();
this.startRow = 0;
this.endRow = list.size() > 0 ? list.size() - 1 : 0;
}
if (list instanceof Collection) {
this.navigatePages = navigatePages;
this.calcNavigatepageNums();
this.calcPage();
this.judgePageBoudary();
}
}
private void calcNavigatepageNums() {
int i;
if (this.pages <= this.navigatePages) {
this.navigatepageNums = new int[this.pages];
for(i = 0; i < this.pages; ++i) {
this.navigatepageNums[i] = i + 1;
}
} else {
this.navigatepageNums = new int[this.navigatePages];
i = this.pageNum - this.navigatePages / 2;
int endNum = this.pageNum + this.navigatePages / 2;
int i;
if (i < 1) {
i = 1;
for(i = 0; i < this.navigatePages; ++i) {
this.navigatepageNums[i] = i++;
}
} else if (endNum > this.pages) {
endNum = this.pages;
for(i = this.navigatePages - 1; i >= 0; --i) {
this.navigatepageNums[i] = endNum--;
}
} else {
for(i = 0; i < this.navigatePages; ++i) {
this.navigatepageNums[i] = i++;
}
}
}
}
private void calcPage() {
if (this.navigatepageNums != null && this.navigatepageNums.length > 0) {
this.navigateFirstPage = this.navigatepageNums[0];
this.navigateLastPage = this.navigatepageNums[this.navigatepageNums.length - 1];
if (this.pageNum > 1) {
this.prePage = this.pageNum - 1;
}
if (this.pageNum < this.pages) {
this.nextPage = this.pageNum + 1;
}
}
}
private void judgePageBoudary() {
this.isFirstPage = this.pageNum == 1;
this.isLastPage = this.pageNum == this.pages || this.pages == 0;
this.hasPreviousPage = this.pageNum > 1;
this.hasNextPage = this.pageNum < this.pages;
}
public int getPageNum() {
return this.pageNum;
}
public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}
public int getPageSize() {
return this.pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getSize() {
return this.size;
}
public void setSize(int size) {
this.size = size;
}
public int getStartRow() {
return this.startRow;
}
public void setStartRow(int startRow) {
this.startRow = startRow;
}
public int getEndRow() {
return this.endRow;
}
public void setEndRow(int endRow) {
this.endRow = endRow;
}
public long getTotal() {
return this.total;
}
public void setTotal(long total) {
this.total = total;
}
public int getPages() {
return this.pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public List<T> getList() {
return this.list;
}
public void setList(List<T> list) {
this.list = list;
}
/** @deprecated */
@Deprecated
public int getFirstPage() {
return this.navigateFirstPage;
}
/** @deprecated */
@Deprecated
public void setFirstPage(int firstPage) {
this.navigateFirstPage = firstPage;
}
public int getPrePage() {
return this.prePage;
}
public void setPrePage(int prePage) {
this.prePage = prePage;
}
public int getNextPage() {
return this.nextPage;
}
public void setNextPage(int nextPage) {
this.nextPage = nextPage;
}
/** @deprecated */
@Deprecated
public int getLastPage() {
return this.navigateLastPage;
}
/** @deprecated */
@Deprecated
public void setLastPage(int lastPage) {
this.navigateLastPage = lastPage;
}
public boolean isIsFirstPage() {
return this.isFirstPage;
}
public void setIsFirstPage(boolean isFirstPage) {
this.isFirstPage = isFirstPage;
}
public boolean isIsLastPage() {
return this.isLastPage;
}
public void setIsLastPage(boolean isLastPage) {
this.isLastPage = isLastPage;
}
public boolean isHasPreviousPage() {
return this.hasPreviousPage;
}
public void setHasPreviousPage(boolean hasPreviousPage) {
this.hasPreviousPage = hasPreviousPage;
}
public boolean isHasNextPage() {
return this.hasNextPage;
}
public void setHasNextPage(boolean hasNextPage) {
this.hasNextPage = hasNextPage;
}
public int getNavigatePages() {
return this.navigatePages;
}
public void setNavigatePages(int navigatePages) {
this.navigatePages = navigatePages;
}
public int[] getNavigatepageNums() {
return this.navigatepageNums;
}
public void setNavigatepageNums(int[] navigatepageNums) {
this.navigatepageNums = navigatepageNums;
}
public int getNavigateFirstPage() {
return this.navigateFirstPage;
}
public int getNavigateLastPage() {
return this.navigateLastPage;
}
public void setNavigateFirstPage(int navigateFirstPage) {
this.navigateFirstPage = navigateFirstPage;
}
public void setNavigateLastPage(int navigateLastPage) {
this.navigateLastPage = navigateLastPage;
}
public String toString() {
StringBuffer sb = new StringBuffer("PageInfo{");
sb.append("pageNum=").append(this.pageNum);
sb.append(", pageSize=").append(this.pageSize);
sb.append(", size=").append(this.size);
sb.append(", startRow=").append(this.startRow);
sb.append(", endRow=").append(this.endRow);
sb.append(", total=").append(this.total);
sb.append(", pages=").append(this.pages);
sb.append(", list=").append(this.list);
sb.append(", prePage=").append(this.prePage);
sb.append(", nextPage=").append(this.nextPage);
sb.append(", isFirstPage=").append(this.isFirstPage);
sb.append(", isLastPage=").append(this.isLastPage);
sb.append(", hasPreviousPage=").append(this.hasPreviousPage);
sb.append(", hasNextPage=").append(this.hasNextPage);
sb.append(", navigatePages=").append(this.navigatePages);
sb.append(", navigateFirstPage=").append(this.navigateFirstPage);
sb.append(", navigateLastPage=").append(this.navigateLastPage);
sb.append(", navigatepageNums=");
if (this.navigatepageNums == null) {
sb.append("null");
} else {
sb.append('[');
for(int i = 0; i < this.navigatepageNums.length; ++i) {
sb.append(i == 0 ? "" : ", ").append(this.navigatepageNums[i]);
}
sb.append(']');
}
sb.append('}');
return sb.toString();
}
}
到這裡,基本就OK了,我再次強調我推薦的那兩個專案,那裡面講的很詳細大佬寫的,強調完畢,揮爪~