减少Java代码中的try-catch块以提高性能

Question

我的任务是减少Java代码中的try-catch块以提高性能。 但是每个try块都在检查一种完全不同的异常以及自定义异常。 如何减少try-catch块。

我的代码的一部分示例如下：-

        // 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

如果在这种情况下每个块的异常类型都不同，则可以将try块加入一个块，然后将多个catch块添加到一个try块中

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

您可以将两个try-catch块更改为一个：

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

我会这样写

 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, 
}

而且我会让调用者处理任何异常。

Answer 4

与C ++不同，try-catch-finally块（异常）是Java的基本组成部分。 它们应该被正确使用和使用。 我也不认为它们对性能有重大影响； 即使您没有抓住它们，它们也将被抛出（最终将被主线程抓住）。 但是出于美学原因，您可以对其进行重新组织，或者将单个方法用于整个方法，如下所示：

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

您还可以考虑处理它们，而不是再次抛出该异常，并在调用堆栈中的每个方法中进行处理（这可能会对性能产生一点影响。）

Answer 5

正如评论所指出的那样，try / catch块的数目不是问题，这是事实，您是如此频繁地击中它们。

假设您已经分析了性能，而实际上正是这种方法给您带来了问题，那么您应该采取显而易见的步骤来避免引发异常（结果是堆栈被解开）。

例如，如果在调用getTestEngine()之后testEngine为null，则不会从该方法返回，但是您将在testEngine.buildTestTaker()之后立即获得NPE，这将导致您的catch块之一被击中。 相反，如果testEngine为null，则应从方法中返回（带有适当的错误代码），以避免堆栈testEngine 。