Decode plus sign in resource attributes

sdk-extensions/autoconfigure/src/main/java/io/opentelemetry/sdk/autoconfigure/ResourceConfiguration.java

@@ -17,8 +17,6 @@
 import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.resources.ResourceBuilder;
-import java.io.UnsupportedEncodingException;
-import java.net.URLDecoder;
 import java.nio.charset.StandardCharsets;
 import java.util.Collections;
 import java.util.HashSet;
@@ -67,18 +65,14 @@ public static Resource createEnvironmentResource() {
    */
   public static Resource createEnvironmentResource(ConfigProperties config) {
     AttributesBuilder resourceAttributes = Attributes.builder();
-    try {
-      for (Map.Entry<String, String> entry : config.getMap(ATTRIBUTE_PROPERTY).entrySet()) {
-        resourceAttributes.put(
-            entry.getKey(),
-            // Attributes specified via otel.resource.attributes follow the W3C Baggage spec and
-            // characters outside the baggage-octet range are percent encoded
-            // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable
-            URLDecoder.decode(entry.getValue(), StandardCharsets.UTF_8.displayName()));
-      }
-    } catch (UnsupportedEncodingException e) {
-      // Should not happen since always using standard charset
-      throw new ConfigurationException("Unable to decode resource attributes.", e);
+    for (Map.Entry<String, String> entry : config.getMap(ATTRIBUTE_PROPERTY).entrySet()) {
+      resourceAttributes.put(
+          entry.getKey(),
+          // Attributes specified via otel.resource.attributes follow the W3C Baggage spec and
+          // characters outside the baggage-octet range are percent encoded
+          // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable
+
+          decodeResourceAttributes(entry.getValue()));
     }
     String serviceName = config.getString(SERVICE_NAME_PROPERTY);
     if (serviceName != null) {
@@ -132,5 +126,35 @@ static Resource filterAttributes(Resource resource, ConfigProperties configPrope
     return builder.build();
   }
 
+  private static String decodeResourceAttributes(String value) {
+    try {
+      if (value.indexOf('%') < 0) {
+        return value;
+      }
+
+      int n = value.length();
+      byte[] bytes = new byte[n];
+      int pos = 0;
+
+      for (int i = 0; i < n; i++) {
+        char c = value.charAt(i);
+        if (c == '%' && i + 2 < n) {
+          int d1 = Character.digit(value.charAt(i + 1), 16);
+          int d2 = Character.digit(value.charAt(i + 2), 16);
+          if (d1 != -1 && d2 != -1) {
+            bytes[pos++] = (byte) ((d1 << 4) + d2);
+            i += 2;
+            continue;
+          }
+        }
+        // Keep '+' as '+' and any other non-encoded chars
+        bytes[pos++] = (byte) c;
+      }
+      return new String(bytes, 0, pos, StandardCharsets.UTF_8);
+    } catch (RuntimeException e) {
+      throw new ConfigurationException("Failed to decode resource attributes: " + value, e);
+    }
+  }
+
   private ResourceConfiguration() {}
 }

sdk-extensions/autoconfigure/src/test/java/io/opentelemetry/sdk/autoconfigure/ResourceConfigurationTest.java

@@ -50,6 +50,93 @@ void customConfigResourceWithDisabledKeys() {
                 .build());
   }
 
+  @Test
+  void decodePlusSignInCustomConfigResource() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.service.name", "my-app");
+    props.put(
+        "otel.resource.attributes", "food=cheese+cake,drink=juice,animal=  ,color=,shape=square");
+
+    assertThat(
+            ResourceConfiguration.configureResource(
+                DefaultConfigProperties.create(props, componentLoader),
+                SpiHelper.create(ResourceConfigurationTest.class.getClassLoader()),
+                (r, c) -> r))
+        .isEqualTo(
+            Resource.getDefault().toBuilder()
+                .put(stringKey("service.name"), "my-app")
+                .put("food", "cheese+cake")
+                .put("drink", "juice")
+                .put("shape", "square")
+                .build());
+  }
+
+  @Test
+  void decodePercentEncodedSpace() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.resource.attributes", "key=hello%20world");
+
+    assertThat(
+            ResourceConfiguration.createEnvironmentResource(
+                DefaultConfigProperties.createFromMap(props)))
+        .isEqualTo(Resource.create(Attributes.of(stringKey("key"), "hello world")));
+  }
+
+  @Test
+  void decodeInvalidPercentEncodingPreservesLiteral() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.resource.attributes", "key=abc%2Gdef");
+
+    assertThat(
+            ResourceConfiguration.createEnvironmentResource(
+                DefaultConfigProperties.createFromMap(props)))
+        .isEqualTo(Resource.create(Attributes.of(stringKey("key"), "abc%2Gdef")));
+  }
+
+  @Test
+  void decodeIncompletePercentEncodingPreservesLiteral() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.resource.attributes", "key=abc%2");
+
+    assertThat(
+            ResourceConfiguration.createEnvironmentResource(
+                DefaultConfigProperties.createFromMap(props)))
+        .isEqualTo(Resource.create(Attributes.of(stringKey("key"), "abc%2")));
+  }
+
+  @Test
+  void decodePercentAtEndPreservesLiteral() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.resource.attributes", "key=abc%");
+
+    assertThat(
+            ResourceConfiguration.createEnvironmentResource(
+                DefaultConfigProperties.createFromMap(props)))
+        .isEqualTo(Resource.create(Attributes.of(stringKey("key"), "abc%")));
+  }
+
+  @Test
+  void decodeMultiplePercentEncodings() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.resource.attributes", "key=a%20b%2Bc%3Dd");
+
+    assertThat(
+            ResourceConfiguration.createEnvironmentResource(
+                DefaultConfigProperties.createFromMap(props)))
+        .isEqualTo(Resource.create(Attributes.of(stringKey("key"), "a b+c=d")));
+  }
+
+  @Test
+  void decodeNoPercentEncoding() {
+    Map<String, String> props = new HashMap<>();
+    props.put("otel.resource.attributes", "key=plain-value");
+
+    assertThat(
+            ResourceConfiguration.createEnvironmentResource(
+                DefaultConfigProperties.createFromMap(props)))
+        .isEqualTo(Resource.create(Attributes.of(stringKey("key"), "plain-value")));
+  }
+
   @Test
   void createEnvironmentResource_Empty() {
     Attributes attributes = ResourceConfiguration.createEnvironmentResource().getAttributes();