如何在Java中的JSON解析器的字符串中转义双引号

Question

I got a string like below:

{
    "test": [
        "",
        "abc",
        "IF(Var218 = "charlie") AND (Var85 ≤ 0) AND (Var207 = \"some value\"; \"du\") THEN Appetency = 1 ",
        "",
        """"
    ]
}

The string will be parsed as a JSON object, now the question is how should I escape some of the double quotes in the string in Java effectively?

The string above is just one example, and please notice not all double quotes in the string should be escaped, only double quotes such as in "charlie" and """" should be escaped, otherwise json parser will not parse the string correctly. Expected result should be like:

{
    "test": [
        "",
        "abc",
        "IF(Var218 = \"charlie\") AND (Var85 ≤ 0) AND (Var207 = \"some value\"; \"du\") THEN Appetency = 1 ",
        "",
        "\"\""
    ]
}

Thanks.

Answer 1

I'm using the Gson library for this. But it looks like this is what you are asking for.

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.reflect.TypeToken;
...
public void stuff()
    {
        List<String> data = new ArrayList<String>();
        data.add("");
        data.add("abc");
        data.add("IF(Var218 = \"charlie\") AND (Var85 &le; 0) AND (Var207 = \"some value\"; \"du\") THEN Appetency = 1 ");
        data.add("\"\"");

        Gson gson = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().create();

        JsonObject test = new JsonObject();
        JsonElement jsonData = gson.toJsonTree(data, new TypeToken<List<String>>(){}.getType());
        test.add("test", jsonData);

        String json = gson.toJson(test);
        System.out.println(json);
    }

This will produce:

{
  "test":[
    "",
    "abc",
    "IF(Var218 = \"charlie\") AND (Var85 ≤ 0) AND (Var207 = \"some value\"; \"du\") THEN Appetency = 1 ",
    "",
    "\"\""
  ]
}

Answer 2

In java you escape " by \\" and the same goes for JSON. The problem is that \\" does not include a backward slash, so you need to escape that as well:

String json = "hello \\\"world\\\""; // hello "world"

Notice the three (3) backwards slash.

Answer 3

I don;t see the point bacause you are escaping your cdouble quoted correct

"\"\"" // this will produce ""

So simple before each " place one \\

Answer 4

The following algorithm should work with the JSON String in input

String progress = "";
for(int c = 0; c < input.length(); c++){
    char ch = input.charAt(c);
    if(ch == '\\'){    // Skip if the next character is already escaped
        c++;
        continue;
    }
    if(ch == '\"') progress += "\\\""; // Results in \"
    else progress += ch;    // Add the character to progress
}

The escaped String is now in progress