工具类
常用工具类： 1.POI工具类： import org.apache.poi.hssf.usermodel.HSSFWorkbook; import org.apache.poi.ss.usermodel.Cell; import org.apache.poi.ss.usermodel.Row; import org.apache.poi.ss.usermodel.Sheet; import org.apache.poi.ss.usermodel.Workbook; import org.apache.poi.xssf.usermodel.XSSFWorkbook; import org.springframework.web.multipart.MultipartFile; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.List; public class POIUtils { private final static String xls = "xls"; private final static String xlsx = "xlsx"; private final static String DATE_FORMAT = "yyyy/MM/dd"; /** * 读入excel文件，解析后返回 * @param file * @throws IOException */ public static List<String[]> readExcel(MultipartFile file) throws IOException { //检查文件 checkFile(file); //获得Workbook工作薄对象 Workbook workbook = getWorkBook(file); //创建返回对象，把每行中的值作为一个数组，所有行作为一个集合返回 List<String[]> list = new ArrayList<String[]>(); if(workbook != null){ for(int sheetNum = 0;sheetNum < workbook.getNumberOfSheets();sheetNum++){ //获得当前sheet工作表 Sheet sheet = workbook.getSheetAt(sheetNum); if(sheet == null){ continue; } //获得当前sheet的开始行 int firstRowNum = sheet.getFirstRowNum(); //获得当前sheet的结束行 int lastRowNum = sheet.getLastRowNum(); //循环除了第一行的所有行 for(int rowNum = firstRowNum+1;rowNum <= lastRowNum;rowNum++){ //获得当前行 Row row = sheet.getRow(rowNum); if(row == null){ continue; } //获得当前行的开始列 int firstCellNum = row.getFirstCellNum(); //获得当前行的列数 int lastCellNum = row.getPhysicalNumberOfCells(); String[] cells = new String[row.getPhysicalNumberOfCells()]; //循环当前行 for(int cellNum = firstCellNum; cellNum < lastCellNum;cellNum++){ Cell cell = row.getCell(cellNum); cells[cellNum] = getCellValue(cell); } list.add(cells); } } workbook.close(); } return list; } //校验文件是否合法 public static void checkFile(MultipartFile file) throws IOException{ //判断文件是否存在 if(null == file){ throw new FileNotFoundException("文件不存在！"); } //获得文件名 String fileName = file.getOriginalFilename(); //判断文件是否是excel文件 if(!fileName.endsWith(xls) && !fileName.endsWith(xlsx)){ throw new IOException(fileName + "不是excel文件"); } } public static Workbook getWorkBook(MultipartFile file) { //获得文件名 String fileName = file.getOriginalFilename(); //创建Workbook工作薄对象，表示整个excel Workbook workbook = null; try { //获取excel文件的io流 InputStream is = file.getInputStream(); //根据文件后缀名不同(xls和xlsx)获得不同的Workbook实现类对象 if(fileName.endsWith(xls)){ //2003 workbook = new HSSFWorkbook(is); }else if(fileName.endsWith(xlsx)){ //2007 workbook = new XSSFWorkbook(is); } } catch (IOException e) { e.printStackTrace(); } return workbook; } public static String getCellValue(Cell cell){ String cellValue = ""; if(cell == null){ return cellValue; } //如果当前单元格内容为日期类型，需要特殊处理 String dataFormatString = cell.getCellStyle().getDataFormatString(); if(dataFormatString.equals("m/d/yy")){ cellValue = new SimpleDateFormat(DATE_FORMAT).format(cell.getDateCellValue()); return cellValue; } //把数字当成String来读，避免出现1读成1.0的情况 if(cell.getCellType() == Cell.CELL_TYPE_NUMERIC){ cell.setCellType(Cell.CELL_TYPE_STRING); } //判断数据的类型 switch (cell.getCellType()){ case Cell.CELL_TYPE_NUMERIC: //数字 cellValue = String.valueOf(cell.getNumericCellValue()); break; case Cell.CELL_TYPE_STRING: //字符串 cellValue = String.valueOf(cell.getStringCellValue()); break; case Cell.CELL_TYPE_BOOLEAN: //Boolean cellValue = String.valueOf(cell.getBooleanCellValue()); break; case Cell.CELL_TYPE_FORMULA: //公式 cellValue = String.valueOf(cell.getCellFormula()); break; case Cell.CELL_TYPE_BLANK: //空值 cellValue = ""; break; case Cell.CELL_TYPE_ERROR: //故障 cellValue = "非法字符"; break; default: cellValue = "未知类型"; break; } return cellValue; } } 2.日期工具类： import java.text.SimpleDateFormat; import java.util.*; /** * 日期操作工具类 */ public class DateUtils { /** * 日期转换- String -> Date * * @param dateString 字符串时间 * @return Date类型信息 * @throws Exception 抛出异常 */ public static Date parseString2Date(String dateString) throws Exception { if (dateString == null) { return null; } return parseString2Date(dateString, "yyyy-MM-dd"); } /** * 日期转换- String -> Date * * @param dateString 字符串时间 * @param pattern 格式模板 * @return Date类型信息 * @throws Exception 抛出异常 */ public static Date parseString2Date(String dateString, String pattern) throws Exception { if (dateString == null) { return null; } SimpleDateFormat sdf = new SimpleDateFormat(pattern); Date date = sdf.parse(dateString); return date; } /** * 日期转换 Date -> String * * @param date Date类型信息 * @return 字符串时间 * @throws Exception 抛出异常 */ public static String parseDate2String(Date date) throws Exception { if (date == null) { return null; } return parseDate2String(date, "yyyy-MM-dd"); } /** * 日期转换 Date -> String * * @param date Date类型信息 * @param pattern 格式模板 * @return 字符串时间 * @throws Exception 抛出异常 */ public static String parseDate2String(Date date, String pattern) throws Exception { if (date == null) { return null; } SimpleDateFormat sdf = new SimpleDateFormat(pattern); String strDate = sdf.format(date); return strDate; } /** * 获取当前日期的本周一是几号 * * @return 本周一的日期 */ public static Date getThisWeekMonday() { Calendar cal = Calendar.getInstance(); cal.setTime(new Date()); // 获得当前日期是一个星期的第几天 int dayWeek = cal.get(Calendar.DAY_OF_WEEK); if (1 == dayWeek) { cal.add(Calendar.DAY_OF_MONTH, -1); } // 设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一 cal.setFirstDayOfWeek(Calendar.MONDAY); // 获得当前日期是一个星期的第几天 int day = cal.get(Calendar.DAY_OF_WEEK); // 根据日历的规则，给当前日期减去星期几与一个星期第一天的差值 cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day); return cal.getTime(); } /** * 获取当前日期周的最后一天 * * @return 当前日期周的最后一天 */ public static Date getSundayOfThisWeek() { Calendar c = Calendar.getInstance(); int dayOfWeek = c.get(Calendar.DAY_OF_WEEK) - 1; if (dayOfWeek == 0) { dayOfWeek = 7; } c.add(Calendar.DATE, -dayOfWeek + 7); return c.getTime(); } /** * 根据日期区间获取月份列表 * * @param minDate 开始时间 * @param maxDate 结束时间 * @return 月份列表 * @throws Exception */ public static List<String> getMonthBetween(String minDate, String maxDate, String format) throws Exception { ArrayList<String> result = new ArrayList<>(); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM"); Calendar min = Calendar.getInstance(); Calendar max = Calendar.getInstance(); min.setTime(sdf.parse(minDate)); min.set(min.get(Calendar.YEAR), min.get(Calendar.MONTH), 1); max.setTime(sdf.parse(maxDate)); max.set(max.get(Calendar.YEAR), max.get(Calendar.MONTH), 2); SimpleDateFormat sdf2 = new SimpleDateFormat(format); Calendar curr = min; while (curr.before(max)) { result.add(sdf2.format(curr.getTime())); curr.add(Calendar.MONTH, 1); } return result; } /** * 根据日期获取年度中的周索引 * * @param date 日期 * @return 周索引 * @throws Exception */ public static Integer getWeekOfYear(String date) throws Exception { Date useDate = parseString2Date(date); Calendar cal = Calendar.getInstance(); cal.setTime(useDate); return cal.get(Calendar.WEEK_OF_YEAR); } /** * 根据年份获取年中周列表 * * @param year 年分 * @return 周列表 * @throws Exception */ public static Map<Integer, String> getWeeksOfYear(String year) throws Exception { Date useDate = parseString2Date(year, "yyyy"); Calendar cal = Calendar.getInstance(); cal.setTime(useDate); //获取年中周数量 int weeksCount = cal.getWeeksInWeekYear(); Map<Integer, String> mapWeeks = new HashMap<>(55); for (int i = 0; i < weeksCount; i++) { cal.get(Calendar.DAY_OF_YEAR); mapWeeks.put(i + 1, parseDate2String(getFirstDayOfWeek(cal.get(Calendar.YEAR), i))); } return mapWeeks; } /** * 获取某年的第几周的开始日期 * * @param year 年分 * @param week 周索引 * @return 开始日期 * @throws Exception */ public static Date getFirstDayOfWeek(int year, int week) throws Exception { Calendar c = new GregorianCalendar(); c.set(Calendar.YEAR, year); c.set(Calendar.MONTH, Calendar.JANUARY); c.set(Calendar.DATE, 1); Calendar cal = (GregorianCalendar) c.clone(); cal.add(Calendar.DATE, week * 7); return getFirstDayOfWeek(cal.getTime()); } /** * 获取某年的第几周的结束日期 * * @param year 年份 * @param week 周索引 * @return 结束日期 * @throws Exception */ public static Date getLastDayOfWeek(int year, int week) throws Exception { Calendar c = new GregorianCalendar(); c.set(Calendar.YEAR, year); c.set(Calendar.MONTH, Calendar.JANUARY); c.set(Calendar.DATE, 1); Calendar cal = (GregorianCalendar) c.clone(); cal.add(Calendar.DATE, week * 7); return getLastDayOfWeek(cal.getTime()); } /** * 获取当前时间所在周的开始日期 * * @param date 当前时间 * @return 开始时间 */ public static Date getFirstDayOfWeek(Date date) { Calendar c = new GregorianCalendar(); c.setFirstDayOfWeek(Calendar.SUNDAY); c.setTime(date); c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek()); return c.getTime(); } /** * 获取当前时间所在周的结束日期 * * @param date 当前时间 * @return 结束日期 */ public static Date getLastDayOfWeek(Date date) { Calendar c = new GregorianCalendar(); c.setFirstDayOfWeek(Calendar.SUNDAY); c.setTime(date); c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 6); return c.getTime(); } //获得上周一的日期 public static Date geLastWeekMonday(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(getThisWeekMonday(date)); cal.add(Calendar.DATE, -7); return cal.getTime(); } //获得本周一的日期 public static Date getThisWeekMonday(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); // 获得当前日期是一个星期的第几天 int dayWeek = cal.get(Calendar.DAY_OF_WEEK); if (1 == dayWeek) { cal.add(Calendar.DAY_OF_MONTH, -1); } // 设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一 cal.setFirstDayOfWeek(Calendar.MONDAY); // 获得当前日期是一个星期的第几天 int day = cal.get(Calendar.DAY_OF_WEEK); // 根据日历的规则，给当前日期减去星期几与一个星期第一天的差值 cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day); return cal.getTime(); } //获得下周一的日期 public static Date getNextWeekMonday(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(getThisWeekMonday(date)); cal.add(Calendar.DATE, 7); return cal.getTime(); } //获得今天日期 public static Date getToday(){ return new Date(); } //获得本月一日的日期 public static Date getFirstDay4ThisMonth(){ Calendar calendar = Calendar.getInstance(); calendar.set(Calendar.DAY_OF_MONTH,1); return calendar.getTime(); } //获得本月最后一日的日期 public static Date getLastDay4ThisMonth(){ Calendar calendar = Calendar.getInstance(); calendar.add(Calendar.MONTH, 1); calendar.set(Calendar.DAY_OF_MONTH, 0); return calendar.getTime(); } public static void main(String[] args) { try { System.out.println("本周一" + parseDate2String(getThisWeekMonday())); System.out.println("本月一日" + parseDate2String(getFirstDay4ThisMonth())); } catch (Exception e) { e.printStackTrace(); } } } 3.Jedis工具类： import redis.clients.jedis.Jedis; import redis.clients.jedis.JedisPool; import redis.clients.jedis.JedisPoolConfig; /** * ToDo * * @author Lyle * @date 2019/12/25 */ public class JedisUtils { //创建全局变量以便静态代码块中可以使用 private static JedisPoolConfig jedisPoolConfig; private static JedisPool jedisPool; static { //因为JedisPool只需要创建和配置一次,所以放入静态代码块比较好 jedisPoolConfig = new JedisPoolConfig(); jedisPoolConfig.setMaxTotal(10); //最多连接数量 jedisPoolConfig.setMaxWaitMillis(1000); //等待时间 // 2. 创建JedisPool对象 String host = "127.0.0.1"; int port = 6379; jedisPool = new JedisPool(jedisPoolConfig, host, port); } //对外提供get方法获得jedis,静态方法,类名调用比较好 public static Jedis getJedis(){ // 3. 从JedisPool获得jedis Jedis jedis = jedisPool.getResource(); return jedis; } //释放资源 public static void close(Jedis jedis){ if(jedis != null){ jedis.close(); } } }
4.响应结果工具类： package entity; import java.io.Serializable; /** * 描述 * * @author 三国的包子 * @version 1.0 * @package entity * * @since 1.0 */ public class Result<T> implements Serializable { private boolean flag;//是否成功 private Integer code;//返回码 private String message;//返回消息 private T data;//返回数据 public Result(boolean flag, Integer code, String message, Object data) { this.flag = flag; this.code = code; this.message = message; this.data = (T) data; } public Result(boolean flag, Integer code, String message) { this.flag = flag; this.code = code; this.message = message; } public Result() { this.flag = true; this.code = StatusCode.OK; this.message = "操作成功!"; } public boolean isFlag() { return flag; } public void setFlag(boolean flag) { this.flag = flag; } public Integer getCode() { return code; } public void setCode(Integer code) { this.code = code; } public String getMessage() { return message; } public void setMessage(String message) { this.message = message; } public T getData() { return data; } public void setData(T data) { this.data = data; } }
5.分页返回结果工具类： package entity; import java.util.List; /** * 分页结果类 */ public class PageResult<T> { private Long total;//总记录数 private List<T> rows;//记录 public PageResult(Long total, List<T> rows) { this.total = total; this.rows = rows; } public PageResult() { } public Long getTotal() { return total; } public void setTotal(Long total) { this.total = total; } public List<T> getRows() { return rows; } public void setRows(List<T> rows) { this.rows = rows; } }
6.分页中接收前端参数的工具类： package entity; import java.io.Serializable; import java.util.List; public class Page <T> implements Serializable{ // 页数（第几页） private long currentpage; // 查询数据库里面对应的数据有多少条 private long total;// 从数据库查处的总记录数 // 每页查5条 private int size; // 下页 private int next; private List<T> list; // 最后一页 private int last; private int lpage; private int rpage; //从哪条开始查 private long start; //全局偏移量 public int offsize = 2; public Page() { super(); } /**** * * @param currentpage * @param total * @param pagesize */ public void setCurrentpage(long currentpage,long total,long pagesize) { //可以整除的情况下 long pagecount = total/pagesize; //如果整除表示正好分N页，如果不能整除在N页的基础上+1页 int totalPages = (int) (total%pagesize==0? total/pagesize : (total/pagesize)+1); //总页数 this.last = totalPages; //判断当前页是否越界,如果越界，我们就查最后一页 if(currentpage>totalPages){ this.currentpage = totalPages; }else{ this.currentpage=currentpage; } //计算start this.start = (this.currentpage-1)*pagesize; } //上一页 public long getUpper() { return currentpage>1? currentpage-1: currentpage; } //总共有多少页，即末页 public void setLast(int last) { this.last = (int) (total%size==0? total/size : (total/size)+1); } /**** * 带有偏移量设置的分页 * @param total * @param currentpage * @param pagesize * @param offsize */ public Page(long total,int currentpage,int pagesize,int offsize) { this.offsize = offsize; initPage(total, currentpage, pagesize); } /**** * * @param total 总记录数 * @param currentpage 当前页 * @param pagesize 每页显示多少条 */ public Page(long total,int currentpage,int pagesize) { initPage(total,currentpage,pagesize); } /**** * 初始化分页 * @param total * @param currentpage * @param pagesize */ public void initPage(long total,int currentpage,int pagesize){ //总记录数 this.total = total; //每页显示多少条 this.size=pagesize; //计算当前页和数据库查询起始值以及总页数 setCurrentpage(currentpage, total, pagesize); //分页计算 int leftcount =this.offsize, //需要向上一页执行多少次 rightcount =this.offsize; //起点页 this.lpage =currentpage; //结束页 this.rpage =currentpage; //2点判断 this.lpage = currentpage-leftcount; //正常情况下的起点 this.rpage = currentpage+rightcount; //正常情况下的终点 //页差=总页数和结束页的差 int topdiv = this.last-rpage; //判断是否大于最大页数 /*** * 起点页 * 1、页差<0 起点页=起点页+页差值 * 2、页差>=0 起点和终点判断 */ this.lpage=topdiv<0? this.lpage+topdiv:this.lpage; /*** * 结束页 * 1、起点页<=0 结束页=|起点页|+1 * 2、起点页>0 结束页 */ this.rpage=this.lpage<=0? this.rpage+(this.lpage*-1)+1: this.rpage; /*** * 当起点页<=0 让起点页为第一页 * 否则不管 */ this.lpage=this.lpage<=0? 1:this.lpage; /*** * 如果结束页>总页数 结束页=总页数 * 否则不管 */ this.rpage=this.rpage>last? this.last:this.rpage; } public long getNext() { return currentpage<last? currentpage+1: last; } public void setNext(int next) { this.next = next; } public long getCurrentpage() { return currentpage; } public long getTotal() { return total; } public void setTotal(long total) { this.total = total; } public long getSize() { return size; } public void setSize(int size) { this.size = size; } public long getLast() { return last; } public long getLpage() { return lpage; } public void setLpage(int lpage) { this.lpage = lpage; } public long getRpage() { return rpage; } public void setRpage(int rpage) { this.rpage = rpage; } public long getStart() { return start; } public void setStart(long start) { this.start = start; } public void setCurrentpage(long currentpage) { this.currentpage = currentpage; } /** * @return the list */ public List<T> getList() { return list; } /** * @param list the list to set */ public void setList(List<T> list) { this.list = list; } public static void main(String[] args) { //总记录数 //当前页 //每页显示多少条 int cpage =17; Page page = new Page(1001,cpage,50,7); System.out.println("开始页:"+page.getLpage()+"__当前页："+page.getCurrentpage()+"__结束页"+page.getRpage()+"____总页数："+page.getLast()); } }
手动分页接收数据模型
package com.itheima.mm.entity; import lombok.Data; import java.io.Serializable; import java.util.Map; /** * @author ：yp * @description : 封装查询条件 * @version: 1.0 a=(当前页码-1) */ @Data public class QueryPageBean implements Serializable{ private Integer currentPage; // 页码 private Integer pageSize; //每页记录数 private Map queryParams; //查询条件 private Integer offset; // 分页查询，开始记录下标 /** * 获取分页起始记录位置 * 根据分页页数，计算limit其实记录 * @return */ public Integer getOffset(){ return (currentPage-1)*pageSize; } }
基于pageHelper分页插件的手动分页工具类
import java.util.List; import com.github.pagehelper.PageInfo; /** * * @ClassName: * @Description: 基于com.github.pagehelper分页插件的手动分页 * @author * @date 2020年3月15日 * */ public class PageHelperUtils { /** * * @Title: initPageInfo * @Description: 将整理后需要分页的数据list进行分页显示 * @param pageNum * 当前页 * @param pageSize * 每页显示的数目 * @param list * 逻辑处理之后所需要统计的总数据 * @return PageInfo<T> 返回PageInfo，这是统计数据中当前页需要显示的数据集合（分页数据） */ public static <T> PageInfo<T> initPageInfo(int pageNum, int pageSize, List<T> list) { int total = list.size(); // 默认如果当前页小于0则为第一页 pageNum = pageNum <= 0 ? 1 : pageNum; // 默认如果当前页大于最大的页数为当前页 pageNum = pageNum > (total + pageSize - 1) / pageSize ? (total + pageSize - 1) / pageSize : pageNum; // 将需要分页的数组进行截取处理 int fromIndex = 0; int toIndex = 0; if (total / pageSize == 0 && total % pageSize > 0) { // 表示当前数据只有一页 fromIndex = 0; toIndex = total; } else if (total / pageSize >= 1 && total % pageSize >= 0) { // 超过一页 fromIndex = (pageNum - 1) * pageSize; toIndex = pageNum * pageSize >= total ? total : pageSize * pageNum; } // 真正需要分页显示的数据 List<T> tempList = list.subList(fromIndex, toIndex); // 结果集(每页显示的数据) PageInfo<T> pageInfo = new PageInfo<>(tempList); // 当前页 pageInfo.setPageNum(pageNum); // 每页的数量 pageInfo.setPageSize(pageSize); // 当前页的数量 pageInfo.setSize(tempList.size()); // 当前页面第一个元素在数据库中的行号 pageInfo.setStartRow(0); // 当前页面最后一个元素在数据库中的行号 pageInfo.setEndRow(tempList.size() > 0 ? tempList.size() - 1 : 0); // 总记录数 pageInfo.setTotal(total); // 总页数 pageInfo.setPages((total + pageSize - 1) / pageSize); // 计算导航页 calcNavigatepageNums(pageInfo); // 计算前后页，第一页，最后一页 calcPage(pageInfo); // 判断页面边界 judgePageBoudary(pageInfo); return pageInfo; } /** * 计算导航页 */ private static <T> void calcNavigatepageNums(PageInfo<T> pageInfo) { int pages = pageInfo.getPages(); int navigatePages = pageInfo.getNavigatePages(); int pageNum = pageInfo.getPageNum(); // 当总页数小于或等于导航页码数时 if (pages <= navigatePages) { pageInfo.setNavigatepageNums(new int[pages]); for (int i = 0; i < pages; i++) { pageInfo.getNavigatepageNums()[i] = i + 1; } } else { // 当总页数大于导航页码数时 pageInfo.setNavigatepageNums(new int[navigatePages]); int startNum = pageNum - navigatePages / 2; int endNum = pageNum + navigatePages / 2; if (startNum < 1) { startNum = 1; // (最前navigatePages页 for (int i = 0; i < navigatePages; i++) { pageInfo.getNavigatepageNums()[i] = startNum++; } } else if (endNum > pages) { endNum = pages; // 最后navigatePages页 for (int i = navigatePages - 1; i >= 0; i--) { pageInfo.getNavigatepageNums()[i] = endNum--; } } else { // 所有中间页 for (int i = 0; i < navigatePages; i++) { pageInfo.getNavigatepageNums()[i] = startNum++; } } } } /** * 计算前后页，第一页，最后一页 */ private static <T> void calcPage(PageInfo<T> pageInfo) { int[] navigatepageNums = pageInfo.getNavigatepageNums(); int pageNum = pageInfo.getPageNum(); int pages = pageInfo.getPages(); if (navigatepageNums != null && navigatepageNums.length > 0) { pageInfo.setFirstPage(navigatepageNums[0]); pageInfo.setLastPage(navigatepageNums[navigatepageNums.length - 1]); if (pageNum > 1) { pageInfo.setPrePage(pageNum - 1); } if (pageNum < pages) { pageInfo.setNextPage(pageNum + 1); } } } /** * 判定页面边界 */ private static <T> void judgePageBoudary(PageInfo<T> pageInfo) { int pageNum = pageInfo.getPageNum(); int pages = pageInfo.getPages(); pageInfo.setIsFirstPage(pageNum == 1); pageInfo.setIsLastPage(pageNum == pages); pageInfo.setHasPreviousPage(pageNum > 1); pageInfo.setHasNextPage(pageNum < pages); } }
使用递归调用查询子类
public List<Depart> getChildren(Long id,List<Depart> list){ List<Depart> children=new ArrayList<>(); List<Depart> departs=new ArrayList<>(); if (list!=null&&list.size()>0){ for (Depart depart : list) { if (depart.getPid()==id.longValue()){ children.add(depart); } } } if (children!=null&&children.size()>0){ for (Depart child : children) { List<Depart> departList = getChildren(child.getId(), list); departs.addAll(departList); } } if (children.size()==0){ return new ArrayList<>(); } return children; }
使用递归方法将List集合转换成树形结构的方法
/** * 方法二、 * @param list * @return */ public static List<TreeNode> listToTree(List<TreeNode> list) { //用递归找子。 List<TreeNode> treeList = new ArrayList<TreeNode>(); for (TreeNode tree : list) { if (tree.getPid() == 0) { treeList.add(findChildren(tree, list)); } } return treeList; } private static TreeNode findChildren(TreeNode tree, List<TreeNode> list) { for (TreeNode node : list) { if (node.getPid() == tree.getId()) { if (tree.getChildren() == null) { tree.setChildren(new ArrayList<TreeNode>()); } tree.getChildren().add(findChildren(node, list)); } } return tree; }
树形结构扁平化的方法
/** * 树形结构扁平化，页面展示形成树形结构{@link SomeModel#getDisplayName()} * 先展示自己，再展示自己的下级 * @param tree 具备children的一个列表 */ public List<SomeModel> flatten(List<SomeModel> tree){ List<SomeModel> list = new LinkedList<>(); for (SomeModel someModel : tree) { list.add(someModel); //孩子扁平化 List<SomeModel> children = someModel.getChildren(); if(CollectionUtil.isEmpty(children)){ continue; } List<SomeModel> flatten = flatten(children); list.addAll(flatten); someModel.setChildren(null); } return list; }
json解析工具类
<!-- Jackson Json处理工具包 -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.4.2</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.7.3</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.7.3</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.7.3</version>
</dependency>
package com.taotao.model.utils; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.JavaType; import com.fasterxml.jackson.databind.ObjectMapper; import java.util.List; /** * json工具类 */ public class JsonUtils { // 定义jackson对象 private static final ObjectMapper MAPPER = new ObjectMapper(); /** * 将对象转换成json字符串。 * <p>Title: pojoToJson</p> * <p>Description: </p> * @param data * @return */ public static String objectToJson(Object data) { try { String string = MAPPER.writeValueAsString(data); return string; } catch (JsonProcessingException e) { e.printStackTrace(); } return null; } /** * 将json结果集转化为对象 * * @param jsonData json数据 * @param clazz 对象中的object类型 * @return */ public static <T> T jsonToPojo(String jsonData, Class<T> beanType) { try { T t = MAPPER.readValue(jsonData, beanType); return t; } catch (Exception e) { e.printStackTrace(); } return null; } /** * 将json数据转换成pojo对象list * <p>Title: jsonToList</p> * <p>Description: </p> * @param jsonData * @param beanType * @return */ public static <T>List<T> jsonToList(String jsonData, Class<T> beanType) { JavaType javaType = MAPPER.getTypeFactory().constructParametricType(List.class, beanType); try { List<T> list = MAPPER.readValue(jsonData, javaType); return list; } catch (Exception e) { e.printStackTrace(); } return null; } }
根据文件url下载文件
public class FileDownload { public static void main(String[] args) { try{ downLoadFromUrl("https://ss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=2534506313,1688529724&fm=26&gp=0.jpg", "百度.jpg","d:/"); }catch (Exception e) { // TODO: handle exception } } public static void downLoadFromUrl(String urlStr,String fileName,String savePath) throws IOException { URL url = new URL(urlStr); HttpURLConnection conn = (HttpURLConnection)url.openConnection(); //设置超时间为3秒 conn.setConnectTimeout(3*1000); //防止屏蔽程序抓取而返回403错误 conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)"); //得到输入流 InputStream inputStream = conn.getInputStream(); //获取自己数组 byte[] getData = readInputStream(inputStream); //文件保存位置 File saveDir = new File(savePath); if(!saveDir.exists()){ saveDir.mkdir(); } File file = new File(saveDir+File.separator+fileName); FileOutputStream fos = new FileOutputStream(file); fos.write(getData); if(fos!=null){ fos.close(); } if(inputStream!=null){ inputStream.close(); } System.out.println("info:"+url+" download success"); } /** * 从输入流中获取字节数组 * @param inputStream * @return * @throws IOException */ public static byte[] readInputStream(InputStream inputStream) throws IOException { byte[] buffer = new byte[1024]; int len = 0; ByteArrayOutputStream bos = new ByteArrayOutputStream(); while((len = inputStream.read(buffer)) != -1) { bos.write(buffer, 0, len); } bos.close(); return bos.toByteArray(); } }
