Merge branch '2.7.x'

Closes gh-32576

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/system/OutputCapture.java

@@ -23,6 +23,7 @@ import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Deque;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 
@@ -48,6 +49,12 @@ class OutputCapture implements CapturedOutput {
 
 	private AnsiOutputState ansiOutputState;
 
+	private final AtomicReference<String> out = new AtomicReference<>(null);
+
+	private final AtomicReference<String> err = new AtomicReference<>(null);
+
+	private final AtomicReference<String> all = new AtomicReference<>(null);
+
 	/**
 	 * Push a new system capture session onto the stack.
 	 */
@@ -55,13 +62,15 @@ class OutputCapture implements CapturedOutput {
 		if (this.systemCaptures.isEmpty()) {
 			this.ansiOutputState = AnsiOutputState.saveAndDisable();
 		}
-		this.systemCaptures.addLast(new SystemCapture());
+		clearExisting();
+		this.systemCaptures.addLast(new SystemCapture(this::clearExisting));
 	}
 
 	/**
 	 * Pop the last system capture session from the stack.
 	 */
 	final void pop() {
+		clearExisting();
 		this.systemCaptures.removeLast().release();
 		if (this.systemCaptures.isEmpty() && this.ansiOutputState != null) {
 			this.ansiOutputState.restore();
@@ -97,7 +106,7 @@ class OutputCapture implements CapturedOutput {
 	 */
 	@Override
 	public String getAll() {
-		return get((type) -> true);
+		return get(this.all, (type) -> true);
 	}
 
 	/**
@@ -106,7 +115,7 @@ class OutputCapture implements CapturedOutput {
 	 */
 	@Override
 	public String getOut() {
-		return get(Type.OUT::equals);
+		return get(this.out, Type.OUT::equals);
 	}
 
 	/**
@@ -115,19 +124,35 @@ class OutputCapture implements CapturedOutput {
 	 */
 	@Override
 	public String getErr() {
-		return get(Type.ERR::equals);
+		return get(this.err, Type.ERR::equals);
 	}
 
 	/**
 	 * Resets the current capture session, clearing its captured output.
 	 */
 	void reset() {
+		clearExisting();
 		this.systemCaptures.peek().reset();
 	}
 
-	private String get(Predicate<Type> filter) {
+	void clearExisting() {
+		this.out.set(null);
+		this.err.set(null);
+		this.all.set(null);
+	}
+
+	private String get(AtomicReference<String> existing, Predicate<Type> filter) {
 		Assert.state(!this.systemCaptures.isEmpty(),
 				"No system captures found. Please check your output capture registration.");
+		String result = existing.get();
+		if (result == null) {
+			result = build(filter);
+			existing.compareAndSet(null, result);
+		}
+		return result;
+	}
+
+	String build(Predicate<Type> filter) {
 		StringBuilder builder = new StringBuilder();
 		for (SystemCapture systemCapture : this.systemCaptures) {
 			systemCapture.append(builder, filter);
@@ -141,6 +166,8 @@ class OutputCapture implements CapturedOutput {
 	 */
 	private static class SystemCapture {
 
+		private final Runnable onCapture;
+
 		private final Object monitor = new Object();
 
 		private final PrintStreamCapture out;
@@ -149,7 +176,8 @@ class OutputCapture implements CapturedOutput {
 
 		private final List<CapturedString> capturedStrings = new ArrayList<>();
 
-		SystemCapture() {
+		SystemCapture(Runnable onCapture) {
+			this.onCapture = onCapture;
 			this.out = new PrintStreamCapture(System.out, this::captureOut);
 			this.err = new PrintStreamCapture(System.err, this::captureErr);
 			System.setOut(this.out);
@@ -162,14 +190,17 @@ class OutputCapture implements CapturedOutput {
 		}
 
 		private void captureOut(String string) {
-			synchronized (this.monitor) {
+			capture(new CapturedString(Type.OUT, string));
-				this.capturedStrings.add(new CapturedString(Type.OUT, string));
-			}
 		}
 
 		private void captureErr(String string) {
+			capture(new CapturedString(Type.ERR, string));
+		}
+
+		private void capture(CapturedString e) {
 			synchronized (this.monitor) {
-				this.capturedStrings.add(new CapturedString(Type.ERR, string));
+				this.onCapture.run();
+				this.capturedStrings.add(e);
 			}
 		}
 
@@ -276,7 +307,7 @@ class OutputCapture implements CapturedOutput {
 	/**
 	 * Types of content that can be captured.
 	 */
-	private enum Type {
+	enum Type {
 
 		OUT, ERR
 

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/system/OutputCaptureTests.java

@@ -19,6 +19,7 @@ package org.springframework.boot.test.system;
 import java.io.ByteArrayOutputStream;
 import java.io.PrintStream;
 import java.util.NoSuchElementException;
+import java.util.function.Predicate;
 
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -42,7 +43,7 @@ class OutputCaptureTests {
 
 	private TestPrintStream systemErr;
 
-	private OutputCapture output = new OutputCapture();
+	private TestOutputCapture output = new TestOutputCapture();
 
 	@BeforeEach
 	void replaceSystemStreams() {
@@ -129,38 +130,69 @@ class OutputCaptureTests {
 
 	@Test
 	void getAllReturnsAllCapturedOutput() {
-		this.output.push();
+		pushAndPrint();
-		System.out.print("A");
-		System.err.print("B");
-		System.out.print("C");
 		assertThat(this.output.getAll()).isEqualTo("ABC");
 	}
 
 	@Test
 	void toStringReturnsAllCapturedOutput() {
-		this.output.push();
+		pushAndPrint();
-		System.out.print("A");
-		System.err.print("B");
-		System.out.print("C");
 		assertThat(this.output.toString()).isEqualTo("ABC");
 	}
 
 	@Test
 	void getErrReturnsOnlyCapturedErrOutput() {
-		this.output.push();
+		pushAndPrint();
-		System.out.print("A");
-		System.err.print("B");
-		System.out.print("C");
 		assertThat(this.output.getErr()).isEqualTo("B");
 	}
 
 	@Test
 	void getOutReturnsOnlyCapturedOutOutput() {
+		pushAndPrint();
+		assertThat(this.output.getOut()).isEqualTo("AC");
+	}
+
+	@Test
+	void getAllUsesCache() {
+		pushAndPrint();
+		for (int i = 0; i < 10; i++) {
+			assertThat(this.output.getAll()).isEqualTo("ABC");
+		}
+		assertThat(this.output.buildCount).isEqualTo(1);
+		System.out.print("X");
+		assertThat(this.output.getAll()).isEqualTo("ABCX");
+		assertThat(this.output.buildCount).isEqualTo(2);
+	}
+
+	@Test
+	void getOutUsesCache() {
+		pushAndPrint();
+		for (int i = 0; i < 10; i++) {
+			assertThat(this.output.getOut()).isEqualTo("AC");
+		}
+		assertThat(this.output.buildCount).isEqualTo(1);
+		System.out.print("X");
+		assertThat(this.output.getOut()).isEqualTo("ACX");
+		assertThat(this.output.buildCount).isEqualTo(2);
+	}
+
+	@Test
+	void getErrUsesCache() {
+		pushAndPrint();
+		for (int i = 0; i < 10; i++) {
+			assertThat(this.output.getErr()).isEqualTo("B");
+		}
+		assertThat(this.output.buildCount).isEqualTo(1);
+		System.err.print("X");
+		assertThat(this.output.getErr()).isEqualTo("BX");
+		assertThat(this.output.buildCount).isEqualTo(2);
+	}
+
+	private void pushAndPrint() {
 		this.output.push();
 		System.out.print("A");
 		System.err.print("B");
 		System.out.print("C");
-		assertThat(this.output.getOut()).isEqualTo("AC");
 	}
 
 	static class TestPrintStream extends PrintStream {
@@ -176,4 +208,16 @@ class OutputCaptureTests {
 
 	}
 
+	static class TestOutputCapture extends OutputCapture {
+
+		int buildCount;
+
+		@Override
+		String build(Predicate<Type> filter) {
+			this.buildCount++;
+			return super.build(filter);
+		}
+
+	}
+
 }