issue #31 - Add MDC support: withLoggingContext

Author: oshai

src/main/kotlin/mu/KotlinLoggingMDC.kt

@@ -0,0 +1,24 @@
+package mu
+
+import org.slf4j.MDC
+
+inline fun <T> withLoggingContext(pair: Pair<String, String>, body: () -> T): T =
+    MDC.putCloseable(pair.first, pair.second).use { body() }
+
+inline fun <T> withLoggingContext(vararg pair: Pair<String, String>, body: () -> T): T {
+  try {
+    pair.forEach { MDC.put(it.first, it.second) }
+    return body()
+  } finally {
+    pair.forEach { MDC.remove(it.first) }
+  }
+}
+
+inline fun <T> withLoggingContext(map: Map<String, String>, body: () -> T): T {
+  try {
+    map.forEach { MDC.put(it.key, it.value) }
+    return body()
+  } finally {
+    map.forEach { MDC.remove(it.key) }
+  }
+}

src/test/kotlin/mu/KotlinLoggingMDCTest.kt

@@ -0,0 +1,41 @@
+package mu
+
+import org.junit.Assert.*
+import org.junit.Test
+import org.slf4j.MDC
+
+class KotlinLoggingMDCTest {
+
+  @Test
+  fun `simple pair withLoggingContext`() {
+    assertNull(MDC.get("a"))
+    withLoggingContext("a" to "b") {
+      assertEquals("b", MDC.get("a"))
+    }
+    assertNull(MDC.get("a"))
+  }
+
+  @Test
+  fun `multiple pair withLoggingContext`() {
+    assertNull(MDC.get("a"))
+    assertNull(MDC.get("c"))
+    withLoggingContext("a" to "b", "c" to "d") {
+      assertEquals("b", MDC.get("a"))
+      assertEquals("d", MDC.get("c"))
+    }
+    assertNull(MDC.get("a"))
+    assertNull(MDC.get("c"))
+  }
+
+  @Test
+  fun `map withLoggingContext`() {
+    assertNull(MDC.get("a"))
+    assertNull(MDC.get("c"))
+    withLoggingContext(mapOf("a" to "b", "c" to "d")) {
+      assertEquals("b", MDC.get("a"))
+      assertEquals("d", MDC.get("c"))
+    }
+    assertNull(MDC.get("a"))
+    assertNull(MDC.get("c"))
+  }
+}