我正在创建一个通过JSON与服务器通信的应用程序。用户可以输入服务器的地址，并且当用户输入错误的链接时我想提供受控的行为。我不想通过捕捉一般异常来隐藏问题，我想抓住具体的一个，但我无法弄清楚如何。
当用户输入错误的链接时，这是一个日志：
01-19 00:08:10.205: W/dalvikvm(12576): threadid=12: thread exiting with uncaught exception (group=0x410af2a0)
01-19 00:08:10.220: E/AndroidRuntime(12576): FATAL EXCEPTION: AsyncTask #1
01-19 00:08:10.220: E/AndroidRuntime(12576): java.lang.RuntimeException: An error occured while executing doInBackground()
01-19 00:08:10.220: E/AndroidRuntime(12576): at android.os.AsyncTask$3.done(AsyncTask.java:299)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
01-19 00:08:10.220: E/AndroidRuntime(12576): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.lang.Thread.run(Thread.java:856)
01-19 00:08:10.220: E/AndroidRuntime(12576): Caused by: java.lang.IllegalStateException: Target host must not be null, or set in parameters. scheme=null, host=null, path=aaaaaasss
01-19 00:08:10.220: E/AndroidRuntime(12576): at org.apache.http.impl.client.DefaultRequestDirector.determineRoute(DefaultRequestDirector.jav a:591)
01-19 00:08:10.220: E/AndroidRuntime(12576): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:293)
01-19 00:08:10.220: E/AndroidRuntime(12576): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:670)
01-19 00:08:10.220: E/AndroidRuntime(12576): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:509)
01-19 00:08:10.220: E/AndroidRuntime(12576): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
01-19 00:08:10.220: E/AndroidRuntime(12576): at pl.mosek.micro.JSONParser.makeHttpRequestJSONObject(JSONParser.java:62)
01-19 00:08:10.220: E/AndroidRuntime(12576): at pl.mosek.micro.SignInActivity$UserLoginTask.doInBackground(SignInActivity.java:287)
01-19 00:08:10.220: E/AndroidRuntime(12576): at pl.mosek.micro.SignInActivity$UserLoginTask.doInBackground(SignInActivity.java:1)
01-19 00:08:10.220: E/AndroidRuntime(12576): at android.os.AsyncTask$2.call(AsyncTask.java:287)
01-19 00:08:10.220: E/AndroidRuntime(12576): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
01-19 00:08:10.220: E/AndroidRuntime(12576): ... 5 more
这是JSONParser类：
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static JSONArray jArray = null;
static String json = "";
private boolean started = false;
private boolean finished = false;
public static String getJson() {
return json;
}
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequestJSONObject(String url, String method,
List<NameValuePair> params) {
finished = false;
started = true;
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
started = false;
finished = true;
// return JSON String
return jObj;
}
public JSONArray makeHttpRequestJSONArray(String url, String method,
List<NameValuePair> params) {
finished = false;
started = true;
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jArray = new JSONArray(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
started = false;
finished = true;
// return JSON String
return jArray;
}
public boolean isStarted() {
return started;
}
public boolean isFinished() {
return finished;
}
}
我应该怎样做以捕捉特定的例外？
答案 0 :(得分：0)
你可以抓住：
IllegalStateException (Exception e)
或者您可以在执行请求之前检查错误输入。
答案 1 :(得分：0)
pl.mosek.micro.JSONParser.makeHttpRequestJSONObject(JSONParser.java:62)
我不知道你的线在哪里（62），但你可以看到错误：
目标主机不能为空，或者在参数中设置。方案= NULL， host = null，path = aaaaaasss
我认为你应该在使用前检查null。
在这一行：
httpPost.setEntity(new UrlEncodedFormEntity(params));
params是否为空？
而且几乎很重要，请检查您的InputStream
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
is是否为空？
答案 2 :(得分：0)
您正在以Java无法比较的方式比较字符串。
应该是：
if ("POST".equals(method))
你们都没有评价为真，所以你没有设置URL而HTTP对象也在窒息。