• springmvc+jpa实现分页的两种方式


    1.工具类

    public final class QueryTool {
        public static PageRequest buildPageRequest(int pageNumber, int pageSize, String sortType){
            Sort sort = null;
            if("auto".equals(sortType)) {
                sort = new Sort(Direction.DESC, "ctime");
            } else {
                sort = new Sort(Direction.DESC, "ctime");
            }
            
            return new PageRequest(pageNumber, pageSize, sort);
        }
        
        public static <T> Specification<T> buildSpecification(Map<String, Object> searchParams, Class<T> domainClass){
            Map<String, SearchFilter> filters = SearchFilter.parse(searchParams);
            Specification<T> spec = DynamicSpecifications.bySearchFilter(filters.values(), domainClass);
            return spec;
        }
    }

    2.Service类(只给出CommentService)

    @Service
    public class CommentService {
        @Autowired
        private CommentDao commentDao;
        
        @Transactional
        public void addComment(Comment comment) {
            if(comment == null) return;
            commentDao.save(comment);
        }
        
        @Transactional
        public Page<Comment> findAllComments(String problemId, PageRequest pageable){
            Page<Comment> page = commentDao.findAllCommentsByProblemId(problemId, pageable);
            return page;
        }
    }

    3.repository类(problem 和 comment 属于 一对多 的关系)

    @Repository
    public interface CommentDao extends JpaSpecificationExecutor<Comment>,
        PagingAndSortingRepository<Comment, String> {
        
        @Query("select c from Comment c where c.problem.problemid = ?1")
        public Page<Comment> findAllCommentsByProblemId(String problemId, Pageable pageable);
    }

     4.Controller类

      第一种方式

    @Controller
    public class ProblemController {
        
        @Autowired
        private ProblemService problemService;
        
        @Autowired
        private CommentService commentService;
        
        @RequestMapping(value="getCurProblemComments")
        @ResponseBody
        public String getCurProblemComments(String problemName, @RequestParam(value = "pn", defaultValue = "1") int pageNumber,
                @RequestParam(value = "ps", defaultValue = "4") int pageSize,
                @RequestParam(value = "sortType", defaultValue = "auto") String sortType){
            JSONObject jsono = new JSONObject();
            try {
                Problem problem = problemService.getProblemByName(problemName);
                if(problem == null){
                    problem = problemService.addProblem(problemName);
                }
                PageRequest pageRequest = QueryTool.buildPageRequest(pageNumber, pageSize, sortType);
                //根据题目的id获取所有的评论
                Page<Comment> page = commentService.findAllComments(problem.getProblemid(), pageRequest);
                //对 Comment 这个类中的一些字段进行过滤
                SimplePropertyPreFilter spp = new SimplePropertyPreFilter();
                spp.getExcludes().addAll(Comment.getExcludeString());
                jsono.put("success", true);
                jsono.put("message", JSON.toJSONString(page, spp));
            } catch(Exception e){
                e.printStackTrace();
                jsono.put("success", false);
                jsono.put("message", "inner error.");
            }
            return jsono.toString();
        }
    }

      

      第二种方式,(懒了,有些内容是放在servic中的。)

      通过JpaSpecificationExecutor<T> 的Page<T> findAll(Specification<T> spec, Pageable pageable); 方法(按照指定的规格条件)实现分页查询。

    public String getCurProblemComments(@RequestParam(value = "pn", defaultValue = "1") int pageNumber,
            @RequestParam(value = "ps", defaultValue = "2") int pageSize,
            @RequestParam(value = "sortType", defaultValue = "auto") String sortType, ServletRequest request) {
        Map<String, Object> searchParams = new HashMap<String, Object>();
        searchParams = Servlets.getParametersStartingWith(request, "search_");
        System.out.println(EncodeUtils.toUTF8((String)searchParams.get("LIKE_name")));
        PageRequest pageRequest = QueryTool.buildPageRequest(pageNumber, pageSize, sortType);
        searchParams.put(Operator.EQ + "_dr", "0");//逻辑删除中,字段dr=0表示这条数据没有删除
        Specification<Comment> spec = QueryTool.buildSpecification(searchParams, Comment.class);
        Page<Comment> page = commentDao.findAll(spec, pageRequest);
        return JSON.toJSONString(page);
    }

      其中,Specification中的一些比较操作org.springside.modules.persistence.SearchFilter.Operator这个类中找到,如下:

    public static enum Operator {
       EQ, LIKE, GT, LT, GTE, LTE;
    }

      前台传递过来的参数名称中可以包含 Operator 中的一些操作, 比如参数名称是: search_LIKE_name (search表示要查询时比较, LIKE是比较的操作, name是表的字段名)

    5.java简单实现分页

    分页面板类(MyPagePanel.java)

    public class MyPagePanel extends JPanel{
        private final int PAGE_BTN_NUM = 6;//按钮的数目的最大值, 一定为偶数
        private JButton[] pageBtns = new JButton[PAGE_BTN_NUM];
        private JButton preBtn = new JButton("<<");//前一页
        private JButton nextBtn = new JButton(">>");//后一页
        
        private JButton jumpBtn = new JButton("跳转");
        private JTextField jumpText = new JTextField(5);//输入页号
        private JLabel totPageLabel = new JLabel("共0页");//提示一共多少页
        
        public static final int PAGE_SIZE = 2;
        private CommunicationPanel parentPanel;
        private ChatPanel chatPanel;
        //刷新某页
        public void refreshPage(){
            if(curPage == -1){
                JOptionPane.showMessageDialog(null, "请选择题目,然后再刷新!", "温馨提示",JOptionPane.WARNING_MESSAGE);
            } else {
                requestPage(curPage);
            }
        }
        //请求某页
        public void requestPage(int pageNumber){
            //当前页按钮设为 true
            if(curBtnPos >= 0)
                pageBtns[curBtnPos].setEnabled(true);
            
            JSONObject jsono = new JSONObject();
            jsono.put("problemName", JavaRequest.problemName);
            jsono.put("pageSize", String.valueOf(PAGE_SIZE));
            jsono.put("pageNumber", String.valueOf(pageNumber));
            String data = JavaRequest.sendPost("getCurProblemComments", jsono);
            
            //获取当前题目的 评论记录
            JSONObject result = JSONObject.fromObject(data);
            if((Boolean) result.get("success")){//分页显示
                JSONObject message = JSONObject.fromObject(result.get("message"));
                Map<String, Class<?>> classMap = new HashMap<String, Class<?>>();
                classMap.put("content", MyMessage.class);
                MyPage myPage = (MyPage) JSONObject.toBean(message, MyPage.class, classMap);
                this.updatePage(myPage);
            } else {
                JOptionPane.showMessageDialog(null, result.getString("message"), "温馨提示",JOptionPane.WARNING_MESSAGE);
                if(result.get("returnLogin") != null && (Boolean)result.get("returnLogin")){//如果用户登录超时返回用户登陆界面
                    parentPanel.switchPanel(CommunicationPanel.LOGIN_PANEL);
                }
            }
        }
        //跳转都页面
        private void jumpPage(int pageNumber) throws Exception{
            if(pageNumber < 0 || pageNumber >= totalPages)
                throw new Exception("不存在该页号!");
            requestPage(pageNumber);
        }
        
        public MyPagePanel(CommunicationPanel parentPanelx, ChatPanel chatPanelx){
            this.parentPanel = parentPanelx;
            this.chatPanel = chatPanelx;
            
            preBtn.setEnabled(false);
            this.add(preBtn);
            preBtn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    requestPage(curPage-1);
                }
            });
            
            for(int i=0; i<pageBtns.length; ++i) {
                pageBtns[i] = new JButton();
                this.add(pageBtns[i]);
                pageBtns[i].setVisible(false);
                pageBtns[i].addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        //JButton text 表示的是页号
                        String text = ((JButton)e.getSource()).getText();
                        int pageNumber = Integer.valueOf(text);
                        requestPage(pageNumber);
                    }
                });
            }
            
            nextBtn.setEnabled(false);
            this.add(nextBtn);
            nextBtn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    requestPage(curPage+1);
                }
            });
            
            jumpBtn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    try{
                        if(jumpText.getText().isEmpty()) throw new Exception("页数不能为空!");
                        int pageNumber = Integer.valueOf(jumpText.getText());
                        jumpPage(pageNumber);
                    } catch (Exception ex){
                        ex.printStackTrace();
                        JOptionPane.showMessageDialog(null, "请确定页号是否正确!", "温馨提示",JOptionPane.WARNING_MESSAGE);
                    }
                }
            });
            this.add(totPageLabel);
            this.add(jumpText);
            this.add(jumpBtn);
        }
        private int curPage = -1, totalPages, curBtnPos = -1;
        public void updatePage(MyPage myPage){
            //清除当页面的信息
            chatPanel.getJpChat().setText("");
            //处理接受到的 评论消息
            for(MyMessage message : myPage.getContent()){
                chatPanel.addRecMsg(message.getCcontent(), StyleConstants.ALIGN_LEFT);
            }
            
            curPage = myPage.getNumber();
            totalPages = myPage.getTotalPages();
            totPageLabel.setText("共" + totalPages + "页");
            
            if(curPage == 0) preBtn.setEnabled(false);
            else preBtn.setEnabled(true);
            
            if(curPage == totalPages-1 || totalPages == 0) nextBtn.setEnabled(false);
            else nextBtn.setEnabled(true);
            
            List<Integer> pageNum = new LinkedList<Integer>();
            if(totalPages > 0) {
                int step = PAGE_BTN_NUM/2-1;
                for(int i=step; i>=1; --i) {
                    if(curPage-i>=0)
                        pageNum.add(curPage-i);
                }
                
                pageNum.add(curPage);
                
                for(int i=1; i<=step+1 && curPage+i<totalPages; ++i)
                    pageNum.add(curPage+i);
                
                if(pageNum.size() < PAGE_BTN_NUM){
                    while(pageNum.size() < PAGE_BTN_NUM && pageNum.get(0)-1 >= 0)
                        pageNum.add(0, pageNum.get(0)-1);
                    
                    while(pageNum.size() < PAGE_BTN_NUM && pageNum.get(pageNum.size()-1)+1 < totalPages)
                        pageNum.add(pageNum.get(pageNum.size()-1)+1);
                }
            }
            
            int bi = 0;
            for(int pi=0; pi < pageNum.size(); ++pi, ++bi){
                pageBtns[bi].setText(String.valueOf(pageNum.get(pi)));
                if(pageNum.get(pi) == curPage){
                    curBtnPos = bi;//记录这个按钮的页号值 和 当前页号值相等
                }
            }
            //重新显示按钮
            for(int i=0; i<bi; ++i)
                pageBtns[i].setVisible(true);
                
            //后面这些按钮都是没有 用上的
            for(int i=bi; i < pageBtns.length; ++i){
                pageBtns[i].setVisible(false);
            }
            
            if(totalPages > 0)
                pageBtns[curBtnPos].setEnabled(false);
        }
    }
    View Code

    MyMessage.class

    public class MyMessage{
        private String ccontent;
        private String commentid;
        public String getCcontent() {
            return ccontent;
        }
        public void setCcontent(String ccontent) {
            this.ccontent = ccontent;
        }
        public String getCommentid() {
            return commentid;
        }
        public void setCommentid(String commentid) {
            this.commentid = commentid;
        }
    }
    View Code

    MyPage.class

    public class MyPage{
        private List<MyMessage> content;
        private boolean first;
        private boolean last;
        private int number;
        private int numberOfElements;
        private int size;
        private String totalElements;
        private String sort;
        
        public String getSort() {
            return sort;
        }
    
        public void setSort(String sort) {
            this.sort = sort;
        }
    
        public List<MyMessage> getContent() {
            return content;
        }
    
        public void setContent(List<MyMessage> content) {
            this.content = content;
        }
    
        public boolean isFirst() {
            return first;
        }
    
        public void setFirst(boolean first) {
            this.first = first;
        }
    
        public boolean isLast() {
            return last;
        }
    
        public void setLast(boolean last) {
            this.last = last;
        }
    
        public int getNumber() {
            return number;
        }
    
        public void setNumber(int number) {
            this.number = number;
        }
    
        public int getNumberOfElements() {
            return numberOfElements;
        }
    
        public void setNumberOfElements(int numberOfElements) {
            this.numberOfElements = numberOfElements;
        }
    
        public int getSize() {
            return size;
        }
    
        public void setSize(int size) {
            this.size = size;
        }
    
        public String getTotalElements() {
            return totalElements;
        }
    
        public void setTotalElements(String totalElements) {
            this.totalElements = totalElements;
        }
    
        public int getTotalPages() {
            return totalPages;
        }
    
        public void setTotalPages(int totalPages) {
            this.totalPages = totalPages;
        }
    
    
    
        private int totalPages;
    }
    View Code

      实现思路:

    1. 首先看一下后台的json数据的格式(其中message的值是spring Data JPA分页查询结果的json)

    {"success":true,"message":{"content":[{"ccontent":"hjz 2016-38-11 15:38:21*****宋体|12|0-0-0| *****0$$$$$70#####","commentid":"8ae45d92549da2a801549ec092ce001f"},{"ccontent":"hjz 2016-38-11 15:38:10*****宋体|12|0-0-0|哇哇 *****2$$$$$55#####","commentid":"8ae45d92549da2a801549ec068c7001e"}],"first":true,"last":false,"number":0,"numberOfElements":2,"size":2,"sort":{},"totalElements":8,"totalPages":4}}

    2. 将“message”对应的值转换成MyPage对象,因为MyPage中有一个List<MyMessage>,如果属性中含有复杂的类型,当其中属性有类似List , Map ,ArrayList、自定义的类型,如List<MyMessage> content, 普通的转换会报错:java.lang.ClassCastException: net.sf.ezmorph.bean.MorphDynaBean cannot be cast to XXX,在JSONObject.toBean的时候如果转换的类中有集合,可以先定义Map<String, Class> classMap = new HashMap<String, Class>();在classMap中put你要转换的类中的集合名 。本例中需要将“content”对应的值转换成 MyMessage对象。

    //data为后台的json串
    JSONObject result = JSONObject.fromObject(data);
    if((Boolean) result.get("success")){//分页显示
        JSONObject message = JSONObject.fromObject(result.get("message"));
        Map<String, Class<?>> classMap = new HashMap<String, Class<?>>();
        classMap.put("content", MyMessage.class);
        MyPage myPage = (MyPage) JSONObject.toBean(message, MyPage.class, classMap);
        this.updatePage(myPage);
    }

    3.然后通过分页的信息,简单的实现分页按钮,详情看MyPagePanel.java

  • 相关阅读:
    [Android Studio 权威教程]Windows下安装Android Studio
    iOS:获取图片Alpha图片
    MFC 直线 虚线 折线 圆 椭圆 矩形 弧形
    大北农董事长夫人莫云为何在美国被逮捕?
    【源代码】LinkedHashMap源代码剖析
    前端那些事儿——中文乱码,网页中文乱码,网页乱码,块元素,内联元素
    Struts2通过自己定义拦截器实现登录之后跳转到原页面
    unity3d ngui-TweenRotation-TweenPosition-TweenScale
    分析函数在数据分析中的应用
    Java Collection
  • 原文地址:https://www.cnblogs.com/hujunzheng/p/5477523.html
Copyright © 2020-2023  润新知