減少Java代碼中的try-catch塊以提高性能

Question

我的任務是減少Java代碼中的try-catch塊以提高性能。 但是每個try塊都在檢查一種完全不同的異常以及自定義異常。 如何減少try-catch塊。

我的代碼的一部分示例如下：-

        // Get a test engine and use that to initialize and save the test
        // taker
        TestEngine testEngine = null;
        try {
            testEngine = objFactory.getTestEngine(login.getTestengine());
        } catch (NoTestEngineException e) {
            // Add an error message, then throw the exception to struts to
            // handle
            request.setAttribute("errmsg", "Cannot create test engine: " + login.getTestengine());
            request.setAttribute("errcause", "exception.notestengine.cause");

            throw e;
        }

        //added for null check of variable testEngine
                if(testEngine==null)
                {
                    request.setAttribute("errmsg", "Could not obtain a testengine");
                }

        // Do we need to save the session id?
        String saveSessionId = objFactory.getConfigValue("testengine." + login.getTestengine() + ".recordjessionid", "false");
        String sessionId = null;
        if (saveSessionId.trim().equals("true")) {
            sessionId = request.getSession().getId();
        }



        Testtaker testTaker = null;
        try {
            testTaker = testEngine.buildTestTaker(login, null, sessionId, null, null);
        } catch (Exception e) {
            request.getSession().removeAttribute(ConstantLibrary.SESSION_LOGIN);

            CaslsUtils.outputLoggingData(log_, request);

            // Add an error message, then throw the exception to struts to
            // handle
            request.setAttribute("errmsg", "Cannot build a test taker.");
            request.setAttribute("errcause", "exception.testtakerbuildfailed.cause");

            //throw new NoTestTakerException("Failed to build testtaker.");
            throw e;
        }

Answer 1

如果在這種情況下每個塊的異常類型都不同，則可以將try塊加入一個塊，然后將多個catch塊添加到一個try塊中

try {
    TestEngine testEngine = objFactory.getTestEngine(login.getTestengine());

    //added for null check of variable testEngine
    if(testEngine==null) {
        request.setAttribute("errmsg", "Could not obtain a testengine");
    }

    // Do we need to save the session id?
    String saveSessionId = objFactory.getConfigValue("testengine." + login.getTestengine() + ".recordjessionid", "false");
    String sessionId = null;
    if (saveSessionId.trim().equals("true")) {
        sessionId = request.getSession().getId();
    }

    Testtaker testTaker = testEngine.buildTestTaker(login, null, sessionId, null, null);
} catch (NoTestEngineException e) {
    // Add an error message, then throw the exception to struts to
    // handle
    request.setAttribute("errmsg", "Cannot create test engine: " + login.getTestengine());
    request.setAttribute("errcause", "exception.notestengine.cause");

    throw e;
} catch (Exception e) {
    request.getSession().removeAttribute(ConstantLibrary.SESSION_LOGIN);

    CaslsUtils.outputLoggingData(log_, request);

    // Add an error message, then throw the exception to struts to
    // handle
    request.setAttribute("errmsg", "Cannot build a test taker.");
    request.setAttribute("errcause", "exception.testtakerbuildfailed.cause");

    //throw new NoTestTakerException("Failed to build testtaker.");
    throw e;
}

Answer 2

您可以將兩個try-catch塊更改為一個：

TestEngine testEngine = null;
Testtaker testTaker = null;

try {
  testEngine = objFactory.getTestEngine(login.getTestengine()); 

  String saveSessionId = 
    objFactory.getConfigValue("testengine." + login.getTestengine() + ".recordjessionid", "false");

  String sessionId = saveSessionId.trim().equals("true") ? 
    request.getSession().getId() : null;

  testTaker = testEngine.buildTestTaker(login, null, sessionId, null, null);
}
catch (NoTestEngineException e) {
  // Add an error message, then throw the exception to struts to handle
  request.setAttribute("errmsg", "Cannot create test engine: " + login.getTestengine());
  request.setAttribute("errcause", "exception.notestengine.cause");

  throw e;
}
catch (Exception e) {
  request.getSession().removeAttribute(ConstantLibrary.SESSION_LOGIN);

  CaslsUtils.outputLoggingData(log_, request);

  // Add an error message, then throw the exception to struts to handle
  request.setAttribute("errmsg", "Cannot build a test taker.");
  request.setAttribute("errcause", "exception.testtakerbuildfailed.cause");

  throw e;
}

Answer 3

我會這樣寫

 public void someMethod(... args) throws Exception {
    // taker
    TestEngine testEngine = objFactory.getTestEngine(login.getTestengine());

    // Do we need to save the session id?
    String saveSessionId = objFactory.getConfigValue("testengine." + login.getTestengine() + ".recordjessionid", "false");
    String sessionId = null;
    if (saveSessionId.trim().equals("true")) {
        sessionId = request.getSession().getId();
    }

    Testtaker testTaker =  testEngine.buildTestTaker(login, null, sessionId, null, 
}

而且我會讓調用者處理任何異常。

Answer 4

與C ++不同，try-catch-finally塊（異常）是Java的基本組成部分。 它們應該被正確使用和使用。 我也不認為它們對性能有重大影響； 即使您沒有抓住它們，它們也將被拋出（最終將被主線程抓住）。 但是出於美學原因，您可以對其進行重新組織，或者將單個方法用於整個方法，如下所示：

method() {
 try {
 } catch (Ex1 e1) {
 } catch (Ex2 e2) {
 } finally {
 }
}

您還可以考慮處理它們，而不是再次拋出該異常，並在調用堆棧中的每個方法中進行處理（這可能會對性能產生一點影響。）

Answer 5

正如評論所指出的那樣，try / catch塊的數目不是問題，這是事實，您是如此頻繁地擊中它們。

假設您已經分析了性能，而實際上正是這種方法給您帶來了問題，那么您應該采取顯而易見的步驟來避免引發異常（結果是堆棧被解開）。

例如，如果在調用getTestEngine()之后testEngine為null，則不會從該方法返回，但是您將在testEngine.buildTestTaker()之后立即獲得NPE，這將導致您的catch塊之一被擊中。 相反，如果testEngine為null，則應從方法中返回（帶有適當的錯誤代碼），以避免堆棧testEngine 。