Backport part of #2062

This commit includes fixes for:

 - Spring 33450 - Spring shutdown fails due to IllegalStateException (#2062)
 - [LOG4J2-3618] Fix property source comparator

and review suggestions from #2454.

Author: rgoers

log4j-api-test/src/test/java/org/apache/logging/log4j/util/PropertiesUtilTest.java

@@ -23,10 +23,12 @@
 import static java.time.temporal.ChronoUnit.MINUTES;
 import static java.time.temporal.ChronoUnit.NANOS;
 import static java.time.temporal.ChronoUnit.SECONDS;
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
@@ -36,7 +38,6 @@
 import java.util.Map;
 import java.util.Properties;
 import java.util.stream.Stream;
-import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.parallel.ResourceAccessMode;
@@ -45,19 +46,20 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.junitpioneer.jupiter.Issue;
 import org.junitpioneer.jupiter.ReadsSystemProperty;
 
-public class PropertiesUtilTest {
+class PropertiesUtilTest {
 
     private final Properties properties = new Properties();
 
     @BeforeEach
-    public void setUp() throws Exception {
+    void setUp() throws Exception {
         properties.load(ClassLoader.getSystemResourceAsStream("PropertiesUtilTest.properties"));
     }
 
     @Test
-    public void testExtractSubset() {
+    void testExtractSubset() {
         assertHasAllProperties(PropertiesUtil.extractSubset(properties, "a"));
         assertHasAllProperties(PropertiesUtil.extractSubset(properties, "b."));
         assertHasAllProperties(PropertiesUtil.extractSubset(properties, "c.1"));
@@ -67,7 +69,7 @@ public void testExtractSubset() {
     }
 
     @Test
-    public void testPartitionOnCommonPrefix() {
+    void testPartitionOnCommonPrefix() {
         final Map<String, Properties> parts = PropertiesUtil.partitionOnCommonPrefixes(properties);
         assertEquals(4, parts.size());
         assertHasAllProperties(parts.get("a"));
@@ -85,7 +87,7 @@ private static void assertHasAllProperties(final Properties properties) {
     }
 
     @Test
-    public void testGetCharsetProperty() {
+    void testGetCharsetProperty() {
         final Properties p = new Properties();
         p.setProperty("e.1", StandardCharsets.US_ASCII.name());
         p.setProperty("e.2", "wrong-charset-name");
@@ -130,8 +132,8 @@ static Stream<Arguments> should_properly_parse_duration() {
 
     @ParameterizedTest
     @MethodSource
-    void should_properly_parse_duration(final Duration expected, final String value) {
-        Assertions.assertThat(PropertiesUtil.parseDuration(value)).isEqualTo(expected);
+    void should_properly_parse_duration(final Duration expected, final CharSequence value) {
+        assertThat(PropertiesUtil.parseDuration(value)).isEqualTo(expected);
     }
 
     static List<String> should_throw_on_invalid_duration() {
@@ -142,29 +144,29 @@ static List<String> should_throw_on_invalid_duration() {
 
     @ParameterizedTest
     @MethodSource
-    void should_throw_on_invalid_duration(final String value) {
+    void should_throw_on_invalid_duration(final CharSequence value) {
         assertThrows(IllegalArgumentException.class, () -> PropertiesUtil.parseDuration(value));
     }
 
     @Test
     @ResourceLock(value = Resources.SYSTEM_PROPERTIES, mode = ResourceAccessMode.READ)
-    public void testGetMappedProperty_sun_stdout_encoding() {
+    void testGetMappedProperty_sun_stdout_encoding() {
         final PropertiesUtil pu = new PropertiesUtil(System.getProperties());
         final Charset expected = System.console() == null ? Charset.defaultCharset() : StandardCharsets.UTF_8;
         assertEquals(expected, pu.getCharsetProperty("sun.stdout.encoding"));
     }
 
     @Test
     @ResourceLock(value = Resources.SYSTEM_PROPERTIES, mode = ResourceAccessMode.READ)
-    public void testGetMappedProperty_sun_stderr_encoding() {
+    void testGetMappedProperty_sun_stderr_encoding() {
         final PropertiesUtil pu = new PropertiesUtil(System.getProperties());
         final Charset expected = System.console() == null ? Charset.defaultCharset() : StandardCharsets.UTF_8;
         assertEquals(expected, pu.getCharsetProperty("sun.err.encoding"));
     }
 
     @Test
     @ResourceLock(Resources.SYSTEM_PROPERTIES)
-    public void testNonStringSystemProperties() {
+    void testNonStringSystemProperties() {
         final Object key1 = "1";
         final Object key2 = new Object();
         System.getProperties().put(key1, new Object());
@@ -180,14 +182,32 @@ public void testNonStringSystemProperties() {
 
     @Test
     @ResourceLock(value = Resources.SYSTEM_PROPERTIES, mode = ResourceAccessMode.READ)
-    public void testPublish() {
+    void testPublish() {
         final Properties props = new Properties();
-        final PropertiesUtil util = new PropertiesUtil(props);
+        new PropertiesUtil(props);
         final String value = System.getProperty("Application");
         assertNotNull(value, "System property was not published");
         assertEquals("Log4j", value);
     }
 
+    @Test
+    @ResourceLock(value = Resources.SYSTEM_PROPERTIES, mode = ResourceAccessMode.READ)
+    @Issue("https://github.com/spring-projects/spring-boot/issues/33450")
+    void testBadPropertySource() {
+        final String key = "testKey";
+        final Properties props = new Properties();
+        props.put(key, "test");
+        final PropertiesUtil util = new PropertiesUtil(props);
+        final ErrorPropertySource source = new ErrorPropertySource();
+        util.addPropertySource(source);
+        try {
+            assertEquals("test", util.getStringProperty(key));
+            assertTrue(source.exceptionThrown);
+        } finally {
+            util.removePropertySource(source);
+        }
+    }
+
     private static final String[][] data = {
         {null, "org.apache.logging.log4j.level"},
         {null, "Log4jAnotherProperty"},
@@ -209,7 +229,7 @@ public void testPublish() {
      */
     @Test
     @ResourceLock(value = Resources.SYSTEM_PROPERTIES, mode = ResourceAccessMode.READ)
-    public void testResolvesOnlyLog4jProperties() {
+    void testResolvesOnlyLog4jProperties() {
         final PropertiesUtil util = new PropertiesUtil("Jira3413Test.properties");
         for (final String[] pair : data) {
             assertEquals(pair[0], util.getStringProperty(pair[1]));
@@ -222,7 +242,7 @@ public void testResolvesOnlyLog4jProperties() {
      */
     @Test
     @ReadsSystemProperty
-    public void testLog4jProperty() {
+    void testLog4jProperty() {
         final Properties props = new Properties();
         final String incorrect = "log4j2.";
         final String correct = "not.starting.with.log4j";
@@ -231,4 +251,40 @@ public void testLog4jProperty() {
         final PropertiesUtil util = new PropertiesUtil(props);
         assertEquals(correct, util.getStringProperty(correct));
     }
+
+    @Test
+    void should_support_multiple_sources_with_same_priority() {
+        final int priority = 2003;
+        final String key1 = "propertySource1";
+        final Properties props1 = new Properties();
+        props1.put(key1, "props1");
+        final String key2 = "propertySource2";
+        final Properties props2 = new Properties();
+        props2.put(key2, "props2");
+        final PropertiesUtil util = new PropertiesUtil(new PropertiesPropertySource(props1, priority));
+        util.addPropertySource(new PropertiesPropertySource(props2, priority));
+        assertThat(util.getStringProperty(key1)).isEqualTo("props1");
+        assertThat(util.getStringProperty(key2)).isEqualTo("props2");
+    }
+
+    private static class ErrorPropertySource implements PropertySource {
+        public boolean exceptionThrown = false;
+
+        @Override
+        public int getPriority() {
+            return Integer.MIN_VALUE;
+        }
+
+        @Override
+        public String getProperty(final String key) {
+            exceptionThrown = true;
+            throw new IllegalStateException("Test");
+        }
+
+        @Override
+        public boolean containsProperty(final String key) {
+            exceptionThrown = true;
+            throw new IllegalStateException("Test");
+        }
+    }
 }