Java 使用GSON解析JSON格式？

通过HTTPURLCONNECTION，我能够获得JSON响应，并且使用Writer，我也能够将其保存到output.JSON文件中。但我无法读取output.json的内容，也无法使用GSON直接从url读取内容。使用gson时，我面临的问题很少

public class ConnectToUrlUsingBasicAuthentication {

    public static void main(String[] args) {

        try {
            String webPage = "http://somesite.com/json/server.json";
            //HTTPURLCONNECTION
            URL url = new URL(webPage);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept", "application/json");
            StringBuilder sb = new StringBuilder();
            InputStream is = conn.getInputStream();
            InputStreamReader isr = new InputStreamReader(is,Charset.defaultCharset());
            BufferedReader bufferedReader = new BufferedReader(isr);
            String line;
            while((line = bufferedReader.readLine()) != null) {
                System.out.println("*** BEGIN ***");
                try(Writer writer = new OutputStreamWriter(new FileOutputStream("Output.json") , "UTF-8")){
                    Gson gson = new GsonBuilder().create();
                    gson.toJson(line, writer);
                    System.out.println("Written successfully");
                }
                System.out.println(line);
                System.out.println("*** END ***");
                try(Reader reader = new InputStreamReader(is, "UTF-8")){
                    Gson gson = new GsonBuilder().create();
                    JsonData p = gson.fromJson(reader, JsonData.class);
                    System.out.println(p);
                }
            }

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

在gson.fromjson调用期间传递的另一个类是Jsondata

为变量p打印的值为空

---

有人能帮我用Gson打印变量p中的Json响应吗。

请等到您阅读了整个响应正文之后，再尝试用Gson转换它

try (Writer writer = new OutputStreamWriter(
        new FileOutputStream("Output.json") , "UTF-8")) {
    Gson gson = new GsonBuilder().create();
    while((line = bufferedReader.readLine()) != null) {
         gson.toJson(line, writer);
    }
}
// Now read it.
try (Reader reader = new InputStreamReader(is, "UTF-8")){
    Gson gson = new GsonBuilder().create();
    JsonData p = gson.fromJson(reader, JsonData.class);
    System.out.println(p);
}

---

当您将InputStream写入文件时，您将使用它。也许这就是问题所在。到底是什么错误？你有stacktrace吗？我没有收到任何错误。但是我尝试了使用null而不是JSON内容打印的值。但我仍然面临着获取JSON响应的问题。我得到的是空值

line = {
    "body":
        {"items":[
            {"name":"server","state":"RUNNING","health":"HEALTH_OK"},
            {"name":"server1","state":"RUNNING","health":"HEALTH_OK"},
            {"name":"server2","state":"RUNNING","health":"HEALTH_OK"}
        ]},

    "messages":[]}

try (Writer writer = new OutputStreamWriter(
        new FileOutputStream("Output.json") , "UTF-8")) {
    Gson gson = new GsonBuilder().create();
    while((line = bufferedReader.readLine()) != null) {
         gson.toJson(line, writer);
    }
}
// Now read it.
try (Reader reader = new InputStreamReader(is, "UTF-8")){
    Gson gson = new GsonBuilder().create();
    JsonData p = gson.fromJson(reader, JsonData.class);
    System.out.println(p);
}