Handling Unicode Encoding Issues and Database Transaction Rollback in Java Services

During recent integration testing the author encountered a pitfall related to character encoding and learned about database transaction rollback.

The problem arose because a Python middle‑layer service automatically converted incoming request parameters to Unicode strings, turning the original Chinese text "测试" into its escaped form "\u6d4b\u8bd5" (UTF‑8), which caused confusion when the Java backend received the data.

When bypassing the middle layer and sending requests directly from the front end, the parameters appear correctly, confirming the issue lies in the middle layer's handling.

To resolve the Unicode conversion issue, the following Java method can be used to transform escaped Unicode sequences back to readable strings:

/**
 * 处理Unicode码转成utf-8
 *
 * @param str
 * @return
 */
public static String unicodeToString(String str) {
    Pattern pattern = Pattern.compile("(\\u(\\p{XDigit}{4}))");
    Matcher matcher = pattern.matcher(str);
    char ch;
    while (matcher.find()) {
        String group = matcher.group(2);
        ch = (char) Integer.parseInt(group, 16);
        String group1 = matcher.group(1);
        str = str.replace(group1, ch + Constant.EMPTY);
    }
    return str;
}

For database rollback, the author adds a Spring @Transactional annotation with rollbackFor = Exception.class to the service class, ensuring that if any step in a multi‑step transaction fails, all previous database operations are rolled back.

Example implementation of a user‑addition method with transaction handling and custom exception throwing:

@Override
public int addUser(EditUserBean user) {
    int add = testUserMapper.addUser(user);
    if (add == 1) {
        TestUserCheckBean userCheckBean = new TestUserCheckBean();
        userCheckBean.copyFrom(user);
        TestUserCheckBean bean = new TestUserCheckBean();
        int i = updateUserStatus(userCheckBean);
        if (i != 1 || StringUtils.isEmpty(userCheckBean.getCertificate())) {
            UserStatusException.fail(TestUserCode.CHECK_FAIL.getDesc());
        }
    } else {
        UserStatusException.fail(TestUserCode.ADD_USER_FAIL.getDesc());
    }
    return user.getId();
}

This approach allows the service to roll back both the newly created user record and any related entries when an error such as a failed association occurs, providing a robust error‑handling mechanism.