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 {@Autowiredprivate CommentDao commentDao;@Transactionalpublic void addComment(Comment comment) {if(comment == null) return;commentDao.save(comment);}@Transactionalpublic 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 {@Autowiredprivate ProblemService problemService;@Autowiredprivate CommentService commentService;@RequestMapping(value="getCurProblemComments")@ResponseBodypublic 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 trueif(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() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic void actionPerformed(ActionEvent e) {requestPage(curPage+1);}});jumpBtn.addActionListener(new ActionListener() {@Overridepublic 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

转载于:https://www.cnblogs.com/hujunzheng/p/5477523.html