Java中OutputStreamWriter中的字符串对象与字符串文字

问题描述

我正在向发送JSON字符串的HTTP服务器发出请求.我使用Gson对JSON对象进行序列化和反序列化.今天，我观察到了这种我不理解的怪异行为.

I'm making requests to a HTTP server sending JSON string. I used Gson for serializing and deserializing JSON objects. Today I observed this pretty weird behavior that I don't understand.

我有:

String jsonAsString = gson.toJson(jsonAsObject).replace("\"", "\\\"");
System.out.println(jsonAsString);

确切地输出以下内容:

{\"content\":\"Literal\",\"pos\":{\"left\":20,\"top\":20}}

现在我正在使用从HttpURLConnection获得的OutputStreamWriter来发出带有JSON有效负载的HTTP，PUT请求.前述要求运作良好:

Now I'm using OutputStreamWriter obtained from HttpURLConnection to make HTTP, PUT request with JSON payload. The foregoing request works fine:

os.write("{\"content\":\"Literal\",\"pos\":{\"left\":20,\"top\":20}}");

但是，当我说:

os.write(jsonAsString);

...请求无效(此服务器未返回任何错误，但我可以看到在将JSON作为字符串对象写入时，它没有执行应有的操作).在字符串对象上使用字符串文字时，有什么区别.我在做错什么吗?

...the request doesn't work (this server doesn't return any errors but I can see that when writing JSON as string object it doesn't do what it should). Is there a difference when using string literal over string object. Am I doing something wrong?

以下是代码段:

public static void EditWidget(SurfaceWidget sw, String widgetId) {
        Gson gson = new Gson();
        String jsonWidget = gson.toJson(sw).replace("\"", "\\\"");

        System.out.println(jsonWidget);

        try {
            HttpURLConnection hurl = getConnectionObject("PUT", "http://fltspc.itu.dk/widget/5162b1a0f835c1585e00009e/");
            hurl.connect();
            OutputStreamWriter os = new OutputStreamWriter(hurl.getOutputStream());
            //os.write("{\"content\":\"Literal\",\"pos\":{\"left\":20,\"top\":20}}");
            os.write(jsonWidget);
            os.flush();
            os.close();
            System.out.println(hurl.getResponseCode());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

推荐答案

删除.replace("\"", "\\\"")指令.没必要

在发送JSON字符串 literal 时，您被迫在双引号之前添加斜杠，因为在Java String literal 中，必须对双引号进行转义(否则，它们会被转义).会标记字符串的结尾，而不是在字符串内用双引号引起来.)

You're forced to add slashes before double quotes when you send a JSON String literal because in a Java String literal, double quotes must be escaped (otherwise, they would mark the end of the String instead of being a double quote inside the String).

但是字节码中的实际String不包含这些反斜杠.它们仅在源代码中使用.

But the actual String, in the bytecode, doesn't contain these backslashes. They're only used in the source code.

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