差異處

這裏顯示兩個版本的差異處。

--- java:junit:tech:capture_log4j_output [2018/04/10 14:18]
tony 建立
+++ java:junit:tech:capture_log4j_output [2023/06/25 09:48] (目前版本)
@@ 行 2: / 行 2: @@
 ====== How to verify the Log4j output? ======
 ===== Problem =====
+當功能的測試案例寫完後，就是要開始針對較特殊的案例撰寫單元測試。log錯誤是一種錯誤回報的例外處理機制，而單元測試中，我們該如何捕捉到這些透過log回報的錯誤呢?\\
+\\
+Log4j可以透過ConsoleAppender將訊息給顯示到console上，[[java:junit:tech:capture_systemout|先前文章]]也分享過驗證console內容的方法；然而我們不希望使用者看到這些內容，所以預設的log4j設定檔是不使用ConsoleAppender。\\
+\\
+如果針對測試提供不同的log4j設定檔，也不是那麼的方便，因此我分享給大家另外一種方法，可以將Log4j訊息導到StringBuffer中以做驗證。
 ===== How to? =====
+主要技巧是透過LogManager在測試之前加入WriterAppender，而WriterAppender會使用我給予的OutputStreamWriter:
 <code java>
-	private StringBuffer mSB;
+private StringBuffer mSB;
-	private StringBufferOutputStream mSBOutputStream;
+private StringBufferOutputStream mSBOutputStream;
-	private WriterAppender testAppender;
+private WriterAppender mTestAppender;
-	@Before
+@Before
-	public void setUp() throws Exception {
+public void setUp() throws Exception {
-		mSB = new StringBuffer();
+	mSB = new StringBuffer();
-		mSBOutputStream =  new StringBufferOutputStream(mSB);
+	mSBOutputStream =  new StringBufferOutputStream(mSB);
-		Writer w = new OutputStreamWriter(mSBOutputStream);
-		testAppender = new WriterAppender();
-		testAppender.setLayout(new PatternLayout(PatternLayout.DEFAULT_CONVERSION_PATTERN));
-		testAppender.setName("test");
-		testAppender.activateOptions();
-		testAppender.setWriter(w);
-		LogManager.getLogger(TimeWatcherBuilder.class).addAppender(testAppender);
-	}
-</code>
+	Writer w = new OutputStreamWriter(mSBOutputStream);
+	mTestAppender= new WriterAppender();
+	mTestAppender.setLayout(new PatternLayout(PatternLayout.DEFAULT_CONVERSION_PATTERN));
+	mTestAppender.setName("test");
+	mTestAppender.activateOptions();
+	mTestAppender.setWriter(w);
+	LogManager.getLogger(TimeWatcherBuilder.class).addAppender(mTestAppender);
+}
+</code>
+當待測程式碼使用了log4j，就會透過OutputStreamWriter將內容寫入[[java:junit:tech:capture_systemout|StringBufferOutputStream]]，而StringBufferOutputStream內部有一個StringBuffer記載內容以供之後驗證。\\
+\\
+當測試之後，不能忘記移除測試用的Appender:
 <code java>
-	@After
+@After
-	public void teardown() throws SchedulerException{
+public void teardown() throws SchedulerException{
-		LogManager.getLogger(TimeWatcherBuilder.class).removeAppender(testAppender);
+	LogManager.getLogger(TimeWatcherBuilder.class).removeAppender(mTestAppender);
-	}
+}
 </code>
 ===== Reference =====