add CoroutineThreadLocalAsContextElementTest

src/test/java/com/alibaba/demo/coroutine/CoroutineThreadLocalAsContextElementTest.kt

+package com.alibaba.demo.coroutine
+
+import kotlinx.coroutines.*
+import org.junit.Assert.*
+import org.junit.Test
+
+class CoroutineThreadLocalAsContextElementTest {
+    @Test
+    fun oneThreadContextElement(): Unit = runBlocking {
+        val mainValue = "main-${System.currentTimeMillis()}"
+        val launchValue = "launch-${System.currentTimeMillis()}"
+        val testThread = Thread.currentThread()
+
+        val threadLocal = ThreadLocal<String?>() // declare thread-local variable
+        threadLocal.set(mainValue)
+        println("test thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()}")
+
+        val job = launch(Dispatchers.Default + threadLocal.asContextElement(value = launchValue)) {
+            println("Launch start, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()}")
+            assertEquals(launchValue, threadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+
+            delay(5)
+
+            println("After delay, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()}")
+            assertEquals(launchValue, threadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+
+            val reset = "job-reset-${threadLocal.get()}"
+            threadLocal.set(reset)
+            assertEquals(reset, threadLocal.get())
+
+            delay(5)
+
+            println("After delay set reset, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()}")
+            // !!! After suspended delay function, reset ThreadLocal value is lost !!!
+            // assertEquals(reset, threadLocal.get())
+            assertEquals(launchValue, threadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+        }
+        job.join()
+
+        println("after launch, test thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()}")
+        assertEquals(mainValue, threadLocal.get())
+    }
+
+    @Test
+    fun twoThreadContextElement(): Unit = runBlocking {
+        val mainValue = "main-a-${System.currentTimeMillis()}"
+        val testThread = Thread.currentThread()
+        val anotherMainValue = "main-another-${System.currentTimeMillis()}"
+
+        val threadLocal = ThreadLocal<String?>() // declare thread-local variable
+        val anotherThreadLocal = ThreadLocal<String?>() // declare thread-local variable
+
+        threadLocal.set(mainValue)
+        anotherThreadLocal.set(anotherMainValue)
+        println("test thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+
+        println()
+        val launch1Value = "aLaunch1"
+        launch(Dispatchers.Default + threadLocal.asContextElement(value = launch1Value)) {
+            println("Launch start, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+            assertEquals(launch1Value, threadLocal.get())
+            assertNull(anotherThreadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+
+            delay(5)
+
+            println("After delay, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+            assertEquals(launch1Value, threadLocal.get())
+            assertNull(anotherThreadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+
+            val resetA = "job-reset-${threadLocal.get()}"
+            threadLocal.set(resetA)
+            val resetAnother = "job-reset-${anotherThreadLocal.get()}"
+            anotherThreadLocal.set(resetAnother)
+            println("Before delay set reset, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+
+            delay(5)
+
+            println("After delay set reset, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+            // !!! After suspended delay function, reset ThreadLocal value is lost !!!
+            // assertEquals(resetA, threadLocal.get())
+            assertEquals(launch1Value, threadLocal.get())
+            // !!! After suspended delay, ThreadLocal without ThreadContextElement is not clear !!!
+            assertEquals(resetAnother, anotherThreadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+        }.join()
+
+        println("after launch1, test thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+        assertEquals(mainValue, threadLocal.get())
+        assertEquals(anotherMainValue, anotherThreadLocal.get())
+
+        println()
+        val launch2Value = "aLaunch2"
+        val anotherLaunch2Value = "anotherLaunch2"
+        launch(Dispatchers.Default + threadLocal.asContextElement(value = launch2Value) + anotherThreadLocal.asContextElement(value = anotherLaunch2Value)) {
+            println("Launch start, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+            assertEquals(launch2Value, threadLocal.get())
+            assertEquals(anotherLaunch2Value, anotherThreadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+
+            delay(5)
+
+            println("After delay, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+            assertEquals(launch2Value, threadLocal.get())
+            assertEquals(anotherLaunch2Value, anotherThreadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+
+            val resetA = "job-reset-${threadLocal.get()}"
+            threadLocal.set(resetA)
+            val resetAnother = "job-reset-${anotherThreadLocal.get()}"
+            anotherThreadLocal.set(resetAnother)
+            println("Before delay set reset, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+
+            delay(5)
+
+            println("After delay set reset, current thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+            // !!! After suspended delay function, reset ThreadLocal value is lost !!!
+            // assertEquals(resetA, threadLocal.get())
+            // assertEquals(resetAnother, anotherThreadLocal.get())
+            assertEquals(launch2Value, threadLocal.get())
+            assertEquals(anotherLaunch2Value, anotherThreadLocal.get())
+            assertNotEquals(testThread, Thread.currentThread())
+        }.join()
+
+        println("after launch2, test thread: ${Thread.currentThread()}, thread local value: ${threadLocal.get()} | ${anotherThreadLocal.get()}")
+        assertEquals(mainValue, threadLocal.get())
+        assertEquals(anotherMainValue, anotherThreadLocal.get())
+    }
+}