Polishing.

Improve encapsulation.

See #3338

src/main/java/org/springframework/data/repository/aot/generate/AotQueryMethodGenerationContext.java

@@ -265,7 +265,7 @@ public class AotQueryMethodGenerationContext {
 	 * @return the variable name used in the generated code.
 	 */
 	public String localVariable(String variableName) {
-		return targetMethodMetadata.getLocalVariables().computeIfAbsent(variableName, variableNameFactory::generateName);
+		return targetMethodMetadata.getOrCreateLocalVariable(variableName, variableNameFactory::generateName);
 	}
 
 	/**
@@ -346,7 +346,7 @@ public class AotQueryMethodGenerationContext {
 	/**
 	 * Obtain the {@link ExpressionMarker} for the current method. Will add a local class within the method that can be
 	 * referenced via {@link ExpressionMarker#enclosingMethod()}.
-	 * 
+	 *
 	 * @return the {@link ExpressionMarker} for this particular method.
 	 */
 	public ExpressionMarker getExpressionMarker() {

src/main/java/org/springframework/data/repository/aot/generate/AotRepositoryMethodBuilder.java

@@ -17,6 +17,7 @@ package org.springframework.data.repository.aot.generate;
 
 import java.lang.reflect.Method;
 import java.lang.reflect.TypeVariable;
+import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -25,9 +26,9 @@ import javax.lang.model.element.Modifier;
 
 import org.springframework.javapoet.CodeBlock;
 import org.springframework.javapoet.MethodSpec;
+import org.springframework.javapoet.ParameterSpec;
 import org.springframework.javapoet.TypeName;
 import org.springframework.javapoet.TypeVariableName;
-import org.springframework.util.StringUtils;
 
 /**
  * Builder for AOT repository query methods.
@@ -82,27 +83,38 @@ class AotRepositoryMethodBuilder {
 	public MethodSpec buildMethod() {
 
 		CodeBlock methodBody = contribution.apply(context);
+		MethodSpec.Builder builder = initializeMethodBuilder();
+
+		if (context.getExpressionMarker().isInUse()) {
+			builder.addCode(context.getExpressionMarker().declaration());
+		}
+
+		builder.addCode(methodBody);
+
+		customizer.accept(context, builder);
+
+		return builder.build();
+	}
+
+	private MethodSpec.Builder initializeMethodBuilder() {
 
 		MethodSpec.Builder builder = MethodSpec.methodBuilder(context.getMethod().getName()).addModifiers(Modifier.PUBLIC);
 		builder.returns(TypeName.get(context.getReturnType().getType()));
 
 		TypeVariable<Method>[] tvs = context.getMethod().getTypeParameters();
-
 		for (TypeVariable<Method> tv : tvs) {
 			builder.addTypeVariable(TypeVariableName.get(tv));
 		}
 
+		MethodMetadata methodMetadata = context.getTargetMethodMetadata();
+		Map<String, ParameterSpec> methodArguments = methodMetadata.getMethodArguments();
 		builder.addJavadoc("AOT generated implementation of {@link $T#$L($L)}.", context.getMethod().getDeclaringClass(),
-				context.getMethod().getName(), StringUtils.collectionToCommaDelimitedString(context.getTargetMethodMetadata()
-						.getMethodArguments().values().stream().map(it -> it.type().toString()).collect(Collectors.toList())));
-		context.getTargetMethodMetadata().getMethodArguments().forEach((name, spec) -> builder.addParameter(spec));
-		if(context.getExpressionMarker().isInUse()) {
-			builder.addCode(context.getExpressionMarker().declaration());
-		}
-		builder.addCode(methodBody);
-		customizer.accept(context, builder);
+				context.getMethod().getName(),
+				methodArguments.values().stream().map(it -> it.type().toString()).collect(Collectors.joining(", ")));
 
-		return builder.build();
+		methodArguments.forEach((name, spec) -> builder.addParameter(spec));
+
+		return builder;
 	}
 
 }

src/main/java/org/springframework/data/repository/aot/generate/MethodMetadata.java

@@ -16,13 +16,17 @@
 package org.springframework.data.repository.aot.generate;
 
 import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.function.Function;
 
 import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.DefaultParameterNameDiscoverer;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
@@ -40,8 +44,8 @@ import org.springframework.javapoet.TypeName;
  */
 class MethodMetadata {
 
-	private final Map<String, ParameterSpec> methodArguments = new LinkedHashMap<>();
-	private final Map<String, MethodParameter> methodParameters = new LinkedHashMap<>();
+	private final Map<String, ParameterSpec> methodArguments;
+	private final Map<String, MethodParameter> methodParameters;
 	private final Map<String, String> localVariables = new LinkedHashMap<>();
 	private final ResolvableType actualReturnType;
 	private final ResolvableType returnType;
@@ -50,15 +54,24 @@ class MethodMetadata {
 
 		this.returnType = repositoryInformation.getReturnType(method).toResolvableType();
 		this.actualReturnType = repositoryInformation.getReturnedDomainTypeInformation(method).toResolvableType();
-		this.initParameters(repositoryInformation, method, new DefaultParameterNameDiscoverer());
-	}
 
-	private void initParameters(RepositoryInformation repositoryInformation, Method method,
-			ParameterNameDiscoverer nameDiscoverer) {
+		Map<String, ParameterSpec> methodArguments = new LinkedHashMap<>();
+		Map<String, MethodParameter> methodParameters = new LinkedHashMap<>();
 
 		ResolvableType repositoryInterface = ResolvableType.forClass(repositoryInformation.getRepositoryInterface());
+		ParameterNameDiscoverer nameDiscoverer = new DefaultParameterNameDiscoverer();
+
+		initializeMethodArguments(method, nameDiscoverer, repositoryInterface, methodArguments, methodParameters);
+
+		this.methodArguments = Collections.unmodifiableMap(methodArguments);
+		this.methodParameters = Collections.unmodifiableMap(methodParameters);
+	}
 
-		for (java.lang.reflect.Parameter parameter : method.getParameters()) {
+	private static void initializeMethodArguments(Method method, ParameterNameDiscoverer nameDiscoverer,
+			ResolvableType repositoryInterface, Map<String, ParameterSpec> methodArguments,
+			Map<String, MethodParameter> methodParameters) {
+
+		for (Parameter parameter : method.getParameters()) {
 
 			MethodParameter methodParameter = MethodParameter.forParameter(parameter);
 			methodParameter.initParameterNameDiscovery(nameDiscoverer);
@@ -66,8 +79,14 @@ class MethodMetadata {
 
 			TypeName parameterType = TypeName.get(resolvableParameterType.getType());
 
-			addParameter(ParameterSpec.builder(parameterType, methodParameter.getParameterName()).build());
-			methodParameters.put(methodParameter.getParameterName(), methodParameter);
+			ParameterSpec parameterSpec = ParameterSpec.builder(parameterType, methodParameter.getParameterName()).build();
+
+			if (methodArguments.containsKey(parameterSpec.name())) {
+				throw new IllegalStateException("Parameter with name '" + parameterSpec.name() + "' already exists.");
+			}
+
+			methodArguments.put(parameterSpec.name(), parameterSpec);
+			methodParameters.put(parameterSpec.name(), methodParameter);
 		}
 	}
 
@@ -79,10 +98,6 @@ class MethodMetadata {
 		return actualReturnType;
 	}
 
-	void addParameter(ParameterSpec parameterSpec) {
-		this.methodArguments.put(parameterSpec.name(), parameterSpec);
-	}
-
 	Map<String, ParameterSpec> getMethodArguments() {
 		return methodArguments;
 	}
@@ -105,8 +120,9 @@ class MethodMetadata {
 		return null;
 	}
 
-	Map<String, String> getLocalVariables() {
-		return localVariables;
+	public String getOrCreateLocalVariable(String variableName,
+			Function<? super String, ? extends String> mappingFunction) {
+		return localVariables.computeIfAbsent(variableName, mappingFunction);
 	}
 
 }

src/test/java/org/springframework/data/repository/aot/generate/AotRepositoryMethodBuilderUnitTests.java

@@ -15,10 +15,9 @@
  */
 package org.springframework.data.repository.aot.generate;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.when;
+import static org.assertj.core.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
+import static org.mockito.Mockito.*;
 
 import example.UserRepository;
 import example.UserRepository.User;
@@ -33,11 +32,10 @@ import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 import org.mockito.Mockito;
+
 import org.springframework.core.ResolvableType;
 import org.springframework.data.repository.core.RepositoryInformation;
 import org.springframework.data.util.TypeInformation;
-import org.springframework.javapoet.ParameterSpec;
-import org.springframework.javapoet.ParameterizedTypeName;
 
 /**
  * @author Christoph Strobl
@@ -66,7 +64,6 @@ class AotRepositoryMethodBuilderUnitTests {
 		doReturn(TypeInformation.of(User.class)).when(repositoryInformation).getReturnType(any());
 		doReturn(TypeInformation.of(User.class)).when(repositoryInformation).getReturnedDomainTypeInformation(any());
 		MethodMetadata methodMetadata = new MethodMetadata(repositoryInformation, method);
-		methodMetadata.addParameter(ParameterSpec.builder(String.class, "firstname").build());
 		when(methodGenerationContext.getTargetMethodMetadata()).thenReturn(methodMetadata);
 
 		AotRepositoryMethodBuilder builder = new AotRepositoryMethodBuilder(methodGenerationContext);
@@ -84,8 +81,6 @@ class AotRepositoryMethodBuilderUnitTests {
 		doReturn(TypeInformation.of(User.class)).when(repositoryInformation).getReturnType(any());
 		doReturn(TypeInformation.of(User.class)).when(repositoryInformation).getReturnedDomainTypeInformation(any());
 		MethodMetadata methodMetadata = new MethodMetadata(repositoryInformation, method);
-		methodMetadata
-				.addParameter(ParameterSpec.builder(ParameterizedTypeName.get(List.class, String.class), "firstnames").build());
 		when(methodGenerationContext.getTargetMethodMetadata()).thenReturn(methodMetadata);
 
 		AotRepositoryMethodBuilder builder = new AotRepositoryMethodBuilder(methodGenerationContext);
@@ -104,7 +99,6 @@ class AotRepositoryMethodBuilderUnitTests {
 		doReturn(TypeInformation.of(User.class)).when(repositoryInformation).getReturnType(any());
 		doReturn(TypeInformation.of(User.class)).when(repositoryInformation).getReturnedDomainTypeInformation(any());
 		MethodMetadata methodMetadata = new MethodMetadata(repositoryInformation, method);
-		methodMetadata.addParameter(ParameterSpec.builder(String.class, "firstname").build());
 		when(methodGenerationContext.getTargetMethodMetadata()).thenReturn(methodMetadata);
 		when(methodGenerationContext.getExpressionMarker()).thenReturn(expressionMarker);