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
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