個人日常開發工具、問題收集-有解無憂

一、SpringBoot try…catch回滾事務

方法上添加注解
```
@Transactional
```

標記回滾開始節點

Object savePoint = TransactionAspectSupport.currentTransactionStatus().createSavepoint();

啟動回滾

TransactionAspectSupport.currentTransactionStatus().rollbackToSavepoint(savePoint);

二、MyBatis查詢關聯

mybatis一對多（ofType：關聯表，column：外鍵）

<resultMap id="resultMap" type="com.wade.www.entity.Entity1">
  <result property="id" column="id"/>
    <result property="name" column="name"/>
    <collection
       	property="entity2List"
         column="{entity2Id=id}"
         ofType="com.wade.www.entity.Entity2"
         javaType="ArrayList"
         select="com.wade.www.mapper.Entity2Mapper.queryById">
    </collection>
</resultMap>

三、檔案與String的相互轉換

檔案轉String

private String fileToString(String pathStr) {
        File file = new File(pathStr);
        try {
            FileInputStream fis = new FileInputStream(file);
            ByteArrayOutputStream bos = new ByteArrayOutputStream(1000);
            byte[] b = new byte[1000];
            int n;
            while ((n = fis.read(b)) != -1) {
                bos.write(b, 0, n);
            }
            fis.close();
            byte[] data = bos.toByteArray();
            bos.close();
            return Base64.getEncoder().encodeToString(data);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

String轉檔案

 public static void StringToFile(String base64file, String filePath, String fileName) throws Exception {
        byte[] bytes = Base64.getDecoder().decode(base64file);
        BufferedOutputStream bos = null;
        FileOutputStream fos = null;
        File file;
        try {
            File dir = new File(filePath);
            if (!dir.exists() && !dir.isDirectory()) {// 判斷檔案目錄是否存在
                dir.mkdirs();
            }
            file = new File(filePath + "\\" + fileName);
            fos = new FileOutputStream(file);
            bos = new BufferedOutputStream(fos);
            bos.write(bytes);
        } catch (Exception e) {
            throw new Exception("檔案傳輸失敗！");
        } finally {
            if (bos != null) {
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

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