好用的代码示例

1、在某个字段后面追加固定的一段数据

   mysql：公式：update table_name set field=CONCAT('str',field) where .....

                示例：update app_contract_ info set apply_type=CONCAT('123456',apply_type) where cont_code ='HFFQ'

   oracle：公式： update table_name set field=field||'str' where .....

                示例：update app_contract_ info set apply_type=apply_type||'123456' where cont_code ='HFFQ'

 

linq使用代码示例：

IEnumerable<Tuple3<Map<String, Object>, Map<String, Object>, Map<String, Object>>> join = Linq.asEnumerable(loanList).leftJoin(
        Linq.asEnumerable(payCardList),
        x -> Convert.toString(x.get("loanNo")),
        y -> Convert.toString(y.get("loanNo")),
        Tuple::create)
        .leftJoin(Linq.asEnumerable(resultList),
                x -> Convert.toString(x.getItem1().get("loanNo")),
                y -> Convert.toString(y.get("loanNo")),
                (x, y) -> Tuple.create(x.getItem1(), x.getItem2(), y));

for(Tuple3<Map<String, Object>, Map<String, Object>, Map<String, Object>> tuple : join) {
    Map<String, Object> map1=tuple .getItem1();
    Map<String, Object> map2=tuple .getItem2();
    Map<String, Object> map3=tuple .getItem3();
}

 类型相互转换工具类：https://github.com/Pinshuducha/utils/tree/master/Convert.java

连接处理

Map<String, Object> adConfigByModelIdAndSizeType = this.getAdConfigByModelIdAndSizeType(params);
        if (!HttpUtil.isSuccess(adConfigByModelIdAndSizeType)) {
            return adConfigByModelIdAndSizeType;
        }
        Map<String, Object> body = FormatUtil.getChildMap(adConfigByModelIdAndSizeType, "body");
        List<Map<String, Object>> modelList = HCMapUtils.getChildList(body, "modelList");
        if (HCCollectionUtils.isEmpty(modelList)) {
            return fail("99", "没有返回参数列表");
        }
        Map<String, Object> result = new HashMap<>(2);
        // 将父级元素获取到
        IEnumerable<Map<String, Object>> father = Linq.asEnumerable(modelList).where(item -> "1".equals(item.get("homeLevel")));
        // 获取子级元素获取到
        IEnumerable<IGrouping<String, Map<String, Object>>> child = Linq.asEnumerable(modelList)
                .where(item -> "2".equals(item.get("homeLevel")))
                .groupBy(x -> Convert.toString(x.get("fatherId")));
        IEnumerable<Tuple2<Map<String, Object>, IGrouping<String, Map<String, Object>>>> joinResult = father.leftJoin(child,
                x -> Convert.toString(x.get("id")),
                y -> Convert.toString(y.getKey()),
                Tuple::create);
        List<Map<String, Object>> childItem = joinResult.select(entry -> {
            Map<String, Object> left = entry.getItem1();
            left.put("child", entry.getItem2().toList());
            return left;
        }).toList();
        result.put("modelList", childItem);
        logger.info("最终结果：" + FormatUtil.toJson(result));
        return success(result);

关于数据库表结构主键的操作

可以新增单主键或联合主键；

alter table tablename add constraint pk_tablename primary key (column1,column2,...);

新增主键前要检查预建主键列是否有重复数据：

select column1 from tablenamed group by column1 having count(column1)>1;

linq 源码

https://github.com/timandy/linq

java压缩文件（一般压缩图片）

 注：此方法的入参File oldFile, File newFile 都是可以new File(path)

public static void compressFile(File oldFile, File newFile, Double scale, Long maxSize, Integer widthMax, Integer heightMax) {
	Assert.notNull(oldFile, "oldFile can not be null");
	Assert.notNull(newFile, "oldFile can not be null");
	logger.info(String.format("压缩照片==> srcPath:%s, descPath:%s", oldFile.getAbsolutePath(), newFile.getAbsolutePath()));
	long startTime = System.currentTimeMillis();
	Long compressDefaultSize = Convert.defaultLong(CommonProperties.get("file.compressDefaultSize"), 2 * 1024 * 1024);//2M
	Double compressDefaultScale = Convert.defaultDouble(CommonProperties.get("file.compressDefaultScale"), 0.5);
	maxSize = Convert.defaultLong(maxSize, compressDefaultSize);
	scale = Convert.defaultDouble(scale, compressDefaultScale);
	logger.info(String.format("原照片大小:%s, 压缩标准:%s 单位：byte(B)", oldFile.length(), maxSize));
	widthMax = Convert.defaultInteger(widthMax, 4096);
	heightMax = Convert.defaultInteger(heightMax, 4096);

	Image srcFile = null;
	int width;
	int height;
	try {
		srcFile = ImageIO.read(oldFile);
		width = srcFile.getWidth(null);
		height = srcFile.getHeight(null);
		logger.info(String.format("原照片%s, height:%s", width, height));
	} catch (IOException e) {
		logger.error(ThrowableUtils.getString(e));
		throw new BusinessException(RestUtil.ERROR_INTERNAL_CODE, "压缩文件失败");
	}

	try {
		int count = 0;
		while (oldFile.length() > maxSize || width> widthMax || height> heightMax) {
			logger.info("ompressCount = " + (++count));
			int widthNew = (int) (width * scale); // 源图宽度
			int heightNew = (int) (height * scale); // 源图高度

			String subfix = StringUtils.getFilenameExtension(oldFile.getPath());
			BufferedImage buffImg;
			if (subfix.equals("png")) {
				buffImg = new BufferedImage(widthNew, heightNew, BufferedImage.TYPE_INT_ARGB);
			} else {
				buffImg = new BufferedImage(widthNew, heightNew, BufferedImage.TYPE_INT_RGB);
			}
			Graphics2D graphics = buffImg.createGraphics();
			graphics.setBackground(new Color(255, 255, 255));
			graphics.setColor(new Color(255, 255, 255));
			graphics.fillRect(0, 0, widthNew, heightNew);
			graphics.drawImage(srcFile.getScaledInstance(widthNew, heightNew, Image.SCALE_SMOOTH), 0, 0, null);
			graphics.dispose();
			ImageIO.write(buffImg, subfix, newFile);
			oldFile = newFile;
			srcFile = ImageIO.read(oldFile);
			width = srcFile.getWidth(null);
			height = srcFile.getHeight(null);
		}

	} catch (Exception e) {
		logger.error(ThrowableUtils.getString(e));
		throw new BusinessException(RestUtil.ERROR_INTERNAL_CODE, "压缩文件失败");
	}
	Long timeSpan = System.currentTimeMillis() - startTime;
	logger.debug(String.format("ompressTook:%sms", timeSpan));
	logger.info(String.format("照片压缩后大小:%s 单位：byte(B)", newFile.length()));
	logger.info(String.format("照片压缩后%s, height:%s", width, height));
	return;
}

 参数拼接

按照某种规则（自定义优先级）排序

public void sortLoanList(List<Map<String, Object>> list) {

        Map<String, Integer> hm = new HashMap<>();
        hm.put("1", 1);
        hm.put("2", 2);
        hm.put("3", 3);
        hm.put("01", 4);
        hm.put("02", 5);
        hm.put("03", 6);
        hm.put("04", 7);
        hm.put("05", 8);
        hm.put("06", 9);
        hm.put("20", 10);
        hm.put("22", 11);
        hm.put("23", 12);
        hm.put("24", 13);
        hm.put("AA", 14);
        hm.put("OD", 15);
        hm.put("WS", 16);
        hm.put("30", 17);
        hm.put("31", 18);
        hm.put("92", 19);
        hm.put("93", 20);

        if (list != null) {
            list.sort((Map<String, Object> s1, Map<String, Object> s2) -> {
                String outSts1 = Convert.defaultString(s1.get(ServiceConstant.OUTSTS));
                String outSts2 = Convert.defaultString(s2.get(ServiceConstant.OUTSTS));
                if (hm.containsKey(outSts1) && hm.containsKey(outSts2)) {
                    return hm.get(outSts2) - hm.get(outSts1);
                } else {
                    return 1;
                }
            });
        }
    }

修改表下字段的长度

 alter table 表名 modify (字段名 varchar2(长度 char));

遍历时删其中的元素

 分段更新数据库表的字段示例

begin
  declare
    cursor c_update is
     select rowid row_id
        from 表名 where 字段名 is null;
    v_counter number := 0;
  begin
    for one_row in c_update loop
      v_counter := v_counter + 1;
      update 表名 SET 字段名='01' where rowid = one_row.row_id;
      if (v_counter = 50000) then
        v_counter := 0;
        commit;
      end if;
    end loop;
    commit;
  end;
end;
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