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PageHelper使用

至于怎么使用我想上面提供的两个项目讲的绝逼讲的比我清楚，下面直接进入PageHelper使用实战

首先，集成引入分页插件有下面2种方式，一种是直接下jar包一种是mawen依赖，推荐使用 Maven 方式。

方法一： 直接下载jar包

，由于使用了sql 解析工具，你还需要下载 

方法二： Maven添加依赖

               
    
     com.github.pagehelper
                
    
     pagehelper
                
    
     5.1.2
      
   

1.导入maven依赖分页插件

我这里就采用方法二maven依赖

2.各个情况下xml的配置

情况一：如果是mybatis单独使用PageHelper分页插件的时候，就需要在xml配置中添加如下代码：

情况二：显然，我是这个是ssm项目，mybatis是交由spring的IOC容器管理的，就需要在spring的xml配置中添加如下代码（创建工厂中添加）：

    
        
         
         
             
                  
                   
                       
                            
         
         
          oracle
          
         
          true
          
                         
                    
               
          
     
   

下面用一个图来分析一下两个参数作用：

3.Controller代码编写

上面我们配置完了，至于为什么从controller代码开始是因为controller调用service嘛，这样编写代码更方便快捷！为了看出差别，未分页的controller代码方法如下：

@Controller@RequestMapping("/orders")public class OrdersController {    @Autowired    private IOrdersService ordersService;//查询所有orders未分页   @RequestMapping("/findAll.do")    public ModelAndView findAll() {        ModelAndView mv = new ModelAndView();        List
   
     ordersList = ordersService.findAll();        mv.addObject("ordersList", ordersList);        mv.setViewName("orders-list");        return mv;    }}
   

而采用了分页代码则是如下：

//采用分页代码方法   @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
   
     ordersList = ordersService.findAll(page,size);        //PageInfo就是一个分页Bean        PageInfo pageInfo =new PageInfo(ordersList);        mv.addObject("pageInfo", pageInfo);        mv.setViewName("orders-list");        return mv;    }
   

可以发现多了两个参数分别是page和size

4.Service接口代码编写

public interface IOrdersService {    List
   
     findAll(int page,int size);}
   

5.Service实现类代码编写

在执行sql之前（ServiceImpl），使用PageHelper分页，参数pageNum 是页码值 参数pageSize 代表是每页显示条数。在ServiceImpl中,使用PageHelper分页操作代码如下：

@Servicepublic class OrdersServiceImpl implements IOrdersService {    @Autowired    private IOrdersDao ordersDao;    @Override    public List
   
     findAll(int page,int size) {        //参数pageNum 是页码值   参数pageSize 代表是每页显示条数        PageHelper.startPage(page, size);        return ordersDao.findAll();    }}
   

特别注意：在编写PageHelper分页代码时的 PageHelper.startPage(page, size)这一句必须写在查询方法的上一句，中间不能添加任何代码，否则失效！

6.jsp页面未处理代码

没有更改的jsp页面代码,普通查询关键更改代码块，注意这里接收数据为 ordersList

              
            ...        ...            
   

这下面的代码则是未分页逻辑代码

   
                        
    
                            
     
                                首页                            
                            
     
上一页
                            
     
1
                            
     
2
                            
     
3
                            
     
4
                            
     
5
                            
     
下一页
                            
     
                                尾页                            
                        
    
                    
   
                

7.jsp页面处理后代码

更改后的jsp页面代码,分页查询的关键更改代码块，注意这里接收数据为 ordersList.list

              
            ...        ...            
   

这下面的代码则是分页逻辑代码

   
   
    
        
     
            首页        
        
     
上一页
        
                 
      
${pageNum}
        
             
     
下一页
        
     
            尾页        
    
    
   

8.jsp页面处理前后代码分析

//PageInfo就是一个分页Bean   PageInfo pageInfo =new PageInfo(ordersList);

为了能看到上面的pageInfo源代码，我就把代码贴在下面了

package com.github.pagehelper;import java.io.Serializable;import java.util.Collection;import java.util.List;public class PageInfo
   
     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
    
      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
     
       list) {        this(list, 8);    }    public PageInfo(List
      
        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
       
         getList() {        return this.list;    }    public void setList(List
        
          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(); }}
        
       
      
     
    
   

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