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Only build OutputCapture strings when necessary
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Update `OutputCapture` so that expensive build operations are only
performed when necessary. This update is especially important for Kotlin
users calling `"Expected String" in output` since this results in a call
to Kotlin's `CharSequence.contains` which calls the `length()` and
`charAt()` methods many times.

Closes gh-32033
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@philwebb
philwebb committed Oct 3, 2022
1 parent 75f4d9e commit e917bd0
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Showing 2 changed files with 100 additions and 25 deletions.
53 changes: 42 additions & 11 deletions ...ct/spring-boot-test/src/main/java/org/springframework/boot/test/system/OutputCapture.java
View file
Expand Up @@ -23,6 +23,7 @@
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;

Expand All @@ -48,20 +49,28 @@ 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.
*/
final void push() {
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();
Expand Down Expand Up @@ -97,7 +106,7 @@ public String toString() {
*/
@Override
public String getAll() {
return get((type) -> true);
return get(this.all, (type) -> true);
}

/**
Expand All @@ -106,7 +115,7 @@ public String getAll() {
*/
@Override
public String getOut() {
return get(Type.OUT::equals);
return get(this.out, Type.OUT::equals);
}

/**
Expand All @@ -115,19 +124,35 @@ public String getOut() {
*/
@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);
Expand All @@ -141,6 +166,8 @@ private String get(Predicate<Type> filter) {
*/
private static class SystemCapture {

private final Runnable onCapture;

private final Object monitor = new Object();

private final PrintStreamCapture out;
Expand All @@ -149,7 +176,8 @@ private static class SystemCapture {

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);
Expand All @@ -162,14 +190,17 @@ void release() {
}

private void captureOut(String string) {
synchronized (this.monitor) {
this.capturedStrings.add(new CapturedString(Type.OUT, string));
}
capture(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);
}
}

Expand Down Expand Up @@ -276,7 +307,7 @@ public String toString() {
/**
* Types of content that can be captured.
*/
private enum Type {
enum Type {

OUT, ERR

Expand Down
72 changes: 58 additions & 14 deletions ...ring-boot-test/src/test/java/org/springframework/boot/test/system/OutputCaptureTests.java
View file
Expand Up @@ -19,6 +19,7 @@
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;
Expand All @@ -42,7 +43,7 @@ class OutputCaptureTests {

private TestPrintStream systemErr;

private OutputCapture output = new OutputCapture();
private TestOutputCapture output = new TestOutputCapture();

@BeforeEach
void replaceSystemStreams() {
Expand Down Expand Up @@ -129,38 +130,69 @@ void subSequenceReturnsCapturedSubSequence() {

@Test
void getAllReturnsAllCapturedOutput() {
this.output.push();
System.out.print("A");
System.err.print("B");
System.out.print("C");
pushAndPrint();
assertThat(this.output.getAll()).isEqualTo("ABC");
}

@Test
void toStringReturnsAllCapturedOutput() {
this.output.push();
System.out.print("A");
System.err.print("B");
System.out.print("C");
pushAndPrint();
assertThat(this.output.toString()).isEqualTo("ABC");
}

@Test
void getErrReturnsOnlyCapturedErrOutput() {
this.output.push();
System.out.print("A");
System.err.print("B");
System.out.print("C");
pushAndPrint();
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 {
Expand All @@ -176,4 +208,16 @@ public String toString() {

}

static class TestOutputCapture extends OutputCapture {

int buildCount;

@Override
String build(Predicate<Type> filter) {
this.buildCount++;
return super.build(filter);
}

}

}

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