分享程序员开发的那些事...
更新时间：2022-09-26 09:34:47
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; } }
@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; } }
@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); }
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)。
分页面板类（MyPagePanel.java）
MyMessage.class
MyPage.class
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