java - Gson为什么要给String加斜杠

Question

我实现了一个简单的 HttpServlet。 servlet 接受请求并调用第三方 API 来获取数据，然后发送回数据作为响应。但是，在响应中，JSON 添加了太多斜杠。

有谁知道为什么吗？
下面是我的代码。

public class InstitutionServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        Gson gson = new Gson();

        String city = request.getParameter("city");
        String apiUrl = "https://inventory.data.gov/api/action/datastore_search?resource_id=38625c3d-5388-4c16-a30f-d105432553a4&q=" + city;
        String data = getInstitutions(apiUrl);

        response.setContentType("application/json");
        PrintWriter pw = response.getWriter();
        gson.toJson(data, pw);
    }

    //Get institutions data from API url.
    private String getInstitutions(String apiUrl) {
        StringBuilder institutions = new StringBuilder();

        try {
            URL url = new URL(apiUrl);
            URLConnection urlConnection = url.openConnection();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
            String line;

            while ((line = bufferedReader.readLine()) != null) {
                institutions.append(line).append("\n");
            }

            bufferedReader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

        return institutions.toString();
    }
}

来自API的原始数据https://inventory.data.gov/api/action/datastore_search?resource_id=38625c3d-5388-4c16-a30f-d105432553a4&q=whatever :

{
    "help": "https://inventory.data.gov/api/3/action/help_show?name=datastore_search",
    "success": true,
    "result": {
        "resource_id": "38625c3d-5388-4c16-a30f-d105432553a4",
        "q": "whatever",
        "records": [],
        "_links": {
            "start": "/api/action/datastore_search?q=whatever&resource_id=38625c3d-5388-4c16-a30f-d105432553a4",
            "next": "/api/action/datastore_search?q=whatever&offset=100&resource_id=38625c3d-5388-4c16-a30f-d105432553a4"
        }
    }
}

Servlet 响应中的数据http://localhost:8080/getInstitutions?city=wahtever:

"{\"help\": 
  \"https://inventory.data.gov/api/3/action/help_show?name\u003ddatastore_search\", 
  \"success\": true, 
  \"result\": {
    \"resource_id\": \"38625c3d-5388-4c16-a30f-d105432553a4\", 
    \"q\": \"wahtever\", 
    \"records\": [], 
    \"_links\": {
      \"start\": \"/api/action/datastore_search?q\u003dwahtever\u0026resource_id\u003d38625c3d-5388-4c16-a30f-d105432553a4\", 
      \"next\": \"/api/action/datastore_search?q\u003dwahtever\u0026offset\u003d100\u0026resource_id\u003d38625c3d-5388-4c16-a30f-d105432553a4\"
    }
  }
}\n"

Answer 1

gson.toJson(data, pw) 正在获取字符串 data 并将其转换为 JSON，因此要做到这一点，它将转义所需的所有字符为了创建一个有效的 JSON 字符串。

目前还不清楚为什么在这种情况下需要 Gson，您应该能够直接将 data 写入 PrintWriter 假设其他函数已经返回JSON 格式的字符串。