The use of PageHelper is simple and popular

I've seen many people's PageHelper Use , At first glance, it's so complicated , Tried several times without success , Now it's finally done . The key points have been thickened . The back end is really super simple , I think the front end is complex, so I can paste it directly .
The effect is as shown in the picture

I don't want to use PageInfo Entity classes are written by themselves ,PageHelper It's delicious .

PageHelper Use
Maven Plus dependence ( That is, the guide package )

    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper</artifactId>
      <version>4.2.1</version>
    </dependency>

2. emphasis
One PageHelper.startPage(pageNum,pageSize);
There is another one PageInfo Wrap it up
It's that simple

@Override
    public PageInfo<User> findByPage(Integer pageNum, Integer pageSize) {
    
        PageHelper.startPage(pageNum,pageSize);
        List<User> users = userDAO.selectByExample(null);
        PageInfo<User> pageInfo = new PageInfo<>(users);
        System.out.println(pageInfo);
        return pageInfo ;
    }

3. Later, when retrieving

emphasize getList()!!!
Theoretically getList Is to get a non paged collection {pageNum,pageSize… A lot of …,List{userList}}

But the printing is strange ,list It's the same as before , But it's good when you use it , To the front is userList. It is estimated that toString What's wrong . Someone on the Internet said it was PageHelper Version of the problem , I changed it and still can't solve it .（ Not affecting use ）

    @RequestMapping("findByPage")
    @ResponseBody
    public Map<String,Object> findByPage(@RequestParam(defaultValue = "1") Integer pageNum,@RequestParam(defaultValue = "5") Integer pageSize){
    
        Map<String,Object> resultMap = new HashMap<>();
        try {
    
            PageInfo<User> byPage = userService.findByPage(pageNum, pageSize);
            System.out.println(byPage);
            resultMap.put("page",byPage);
            resultMap.put("userList",byPage.getList());
            resultMap.put("result",true);
        }catch (Exception e){
    
            resultMap.put("result",false);
            resultMap.put("message"," Paging query exception ");
        }
        return resultMap;
    }

4. Front end writing

pageMsg+='<li class="'+(data.page.pageNum==1?'disabled':'')+'"><a onclick="show('+(data.page.hasPreviousPage?data.page.prePage:data.page.pageNum)+')"> The previous page </a></li>';
    for (var i = 1; i<=data.page.pages;i++){
     pageMsg+='<li class="'+(data.page.pageNum==i?'active':'')+'"><a onclick="show('+i+')">'+i+' <span class="sr-only">(current)</span></a></li>';
     }
    pageMsg+='<li class="'+(data.page.isLastPage?'disabled':'')+'"><a onclick="show('+(data.page.hasNextPage?data.page.nextPage:data.page.pageNum)+')"> The next page </a></li>';
$("#byPage").html(pageMsg);