java - 将 JSON 文件写入 UTF-8 编码

Question

我正在编写一种将一些 JSON 写入文件的方法，该方法运行良好。然而，尽管我已将输出设置为 UTF-8，Oxygen无法读取英镑和欧元符号。

Java代码:

Path logFile = Paths.get(this.output_folder + "/" + file.getName().split("\\.")[0] + ".json");
try (BufferedWriter writer = Files.newBufferedWriter(logFile, StandardCharsets.UTF_8)) {
    File fileDir = new File("test.json");
    Writer out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(fileDir), "UTF8"));
    ObjectMapper mapper = new ObjectMapper();
    writer.write(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(all_questions));
}

“all_questions”是 Question 对象的数组列表，由 ObjectMapper 打印为格式化的 JSON 片段。

一些带有井号的示例 JSON 如下所示:

{
      "name" : "RegExRule",
      "field" : "Q039_4",
      "rules" : [ ],
      "fileName" : "s1rules_england_en.xml",
      "error" : null,
      "pattern_match" : {
        "$record.ApplicationData.SiteVisit.VisitContactDetails.ContactOther.PersonName.PersonGivenName" : "^[\\u0000-\\u005F\\u0061-\\u007B\\u007d-\\u007f£€]*$"
      }
}

但是，这是在 Notepad++ 中显示的。在Oxygen中，显示如下:

"pattern_match" : {
        "$record.ApplicationData.SiteVisit.VisitContactDetails.ContactOther.PersonName.PersonGivenName" : "^[\\u0000-\\u005F\\u0061-\\u007B\\u007d-\\u007f£€]*$"
 }

Answer 1

构造OutputStreamWriter对象时，需要使用"UTF-8"作为字符集名称，而不是"UTF8":

new OutputStreamWriter(..., "UTF-8")

或者，使用 StandardCharsets.UTF_8 代替:

new OutputStreamWriter(..., StandardCharsets.UTF_8)

Java 通常不支持读/写 BOM，因此如果您希望 JSON 文件具有 UTF-8 BOM，则必须手动编写一个:

Writer out = ...;
out.write("\uFEFF");
out.write(... json content here ...); 

仅供引用，PrintWriter 可以为您管理OutputStreamWriter 和FileOutputStream 对象:

Writer out = new PrintWriter(fileDir, "UTF-8");

或者:

Writer out = new PrintWriter("test.json", "UTF-8");

最后，为什么您使用 Files.newBufferedWriter() 创建一个 BufferedWriter 却忽略它并手动创建一个辅助 BufferedWriter？为什么不直接使用您已有的 BufferedWriter:

Path logFile = Paths.get(this.output_folder + "/" + file.getName().split("\\.")[0] + ".json");
try (BufferedWriter writer = Files.newBufferedWriter(logFile, StandardCharsets.UTF_8)) {
    writer.write("\uFEFF");
    ObjectMapper mapper = new ObjectMapper();
    writer.write(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(all_questions));
}