FileNotFoundException異常與ObjectMapper在JSON/REST

Question

我已經創建了一個類，提供了一種方法通過REST以獲得應然後deserialised作爲LinkedHashMap的JSON對象。方法如下：

@Override 
public LinkedHashMap refreshStatus(String metricType, String metricPeriod) { 
    ObjectMapper mapper = new ObjectMapper(); 
    LinkedHashMap<String,String> map = null; 

    try { 
     map = mapper.readValue(new File("http://localhost:8081/Metrics/Stats/JSONP/ReceiveData/"+metricType+"/"+metricPeriod+"/?callback="), LinkedHashMap.class); 


    } catch (JsonParseException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
    e.printStackTrace(); 
} 
    return map; 
} 

當我在瀏覽器中輸入一些特定參數的URL，即

http://localhost:8081/Metrics/Stats/JSONP/ReceiveData/Totals/All/?callback= 

我得到一個正確的JSON對象：

{"Boxes":"8","Contracts":"23","Updates":"1","Deactivations":"4","ActiveBoxes":"33","InactiveBoxes":"1","PendingInstallationsContracts":"70","Alerts":"626","PercentsBoxInstalled":"100.0%","Miles":"0"} 

然而，當我運行應用程序並調用該方法，我得到一個FileNotFoudException：

java.io.FileNotFoundException: http:/localhost:8081/Metrics/Stats/JSONP/ReceiveData/Totals/All/?callback= (No such file or directory) 

有誰知道問題出在哪裏？提前致謝！

Answer 1

確實無法在您的計算機上找到該文件。您嘗試在本地文件系統中創建與真實文件相對應的文件對象，並提供URL作爲參數而不是文件系統路徑。

你實際上想要執行HTTP GET，即做類似下面的事情。

urlString = "http://localhost:8081/Metrics/Stats/JSONP/ReceiveData/Totals/All/?callback="; 
URL url = new URL(urlString); 
URLConnection conn = url.openConnection(); 
map = mapper.readValueconn.getInputStream();