Source code
package org.springframework.core; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set; import org.jspecify.annotations.Nullable; import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils; /**
* Defines the algorithm for searching for metadata-associated methods exhaustively
* including interfaces and parent classes while also dealing with parameterized methods
* as well as common scenarios encountered with interface and class-based proxies.
*
* <p>Typically, but not necessarily, used for finding annotated handler methods.
*
* @author Juergen Hoeller
* @author Rossen Stoyanchev
* @author Sam Brannen
* @since 4.2.3
*/
public final class MethodIntrospector {
private MethodIntrospector() {
} /**
* Select methods on the given target type based on the lookup of associated metadata.
* <p>Callers define methods of interest through the {@link MetadataLookup} parameter,
* allowing to collect the associated metadata into the result map.
* @param targetType the target type to search methods on
* @param metadataLookup a {@link MetadataLookup} callback to inspect methods of interest,
* returning non-null metadata to be associated with a given method if there is a match,
* or {@code null} for no match
* @return the selected methods associated with their metadata (in the order of retrieval),
* or an empty map in case of no match
*/ public static <T> Map<Method, T> selectMethods(Class<?> targetType, final MetadataLookup<T> metadataLookup) {
final Map<Method, T> methodMap = new LinkedHashMap<>();
Set<Class<?>> handlerTypes = new LinkedHashSet<>();
Class<?> specificHandlerType = null; if (!Proxy.isProxyClass(targetType)) { specificHandlerType = ClassUtils.getUserClass(targetType); handlerTypes.add(specificHandlerType); } handlerTypes.addAll(ClassUtils.getAllInterfacesForClassAsSet(targetType));
for (Class<?> currentHandlerType : handlerTypes) {
final Class<?> targetClass = (specificHandlerType != null ? specificHandlerType : currentHandlerType);
ReflectionUtils.doWithMethods(currentHandlerType, method -> {
Method specificMethod = ClassUtils.getMostSpecificMethod(method, targetClass);
T result = metadataLookup.inspect(specificMethod);
if (result != null) {
Method bridgedMethod = BridgeMethodResolver.findBridgedMethod(specificMethod);
if (bridgedMethod == specificMethod || bridgedMethod == method ||
bridgedMethod.equals(specificMethod) || bridgedMethod.equals(method) || metadataLookup.inspect(bridgedMethod) == null) {
methodMap.put(specificMethod, result);
}
}
}, ReflectionUtils.USER_DECLARED_METHODS);
}
return methodMap;
}
/**
* Select methods on the given target type based on a filter.
* <p>Callers define methods of interest through the {@code MethodFilter} parameter.
* @param targetType the target type to search methods on
* @param methodFilter a {@code MethodFilter} to help
* recognize handler methods of interest
* @return the selected methods, or an empty set in case of no match
*/ public static Set<Method> selectMethods(Class<?> targetType, final ReflectionUtils.MethodFilter methodFilter) { return selectMethods(targetType,
(MetadataLookup<Boolean>) method -> (methodFilter.matches(method) ? Boolean.TRUE : null)).keySet(); } /**
* Select an invocable method on the target type: either the given method itself
* if actually exposed on the target type, or otherwise a corresponding method
* on one of the target type's interfaces or on the target type itself.
* <p>Matches on user-declared interfaces will be preferred since they are likely
* to contain relevant metadata that corresponds to the method on the target class.
* @param method the method to check
* @param targetType the target type to search methods on
* (typically an interface-based JDK proxy)
* @return a corresponding invocable method on the target type
* @throws IllegalStateException if the given method is not invocable on the given
* target type (typically due to a proxy mismatch)
*/ public static Method selectInvocableMethod(Method method, Class<?> targetType) { if (method.getDeclaringClass().isAssignableFrom(targetType)) {
return method;
} try { String methodName = method.getName(); Class<?>[] parameterTypes = method.getParameterTypes(); for (Class<?> ifc : targetType.getInterfaces()) {
try { return ifc.getMethod(methodName, parameterTypes); } catch (NoSuchMethodException ex) {
// Alright, not on this interface then...
}
} // A final desperate attempt on the proxy class itself...
return targetType.getMethod(methodName, parameterTypes); }
catch (NoSuchMethodException ex) { throw new IllegalStateException(String.format(
"Need to invoke method '%s' declared on target class '%s', " +
"but not found in any interface(s) of the exposed proxy type. " +
"Either pull the method up to an interface or switch to CGLIB " +
"proxies by enforcing proxy-target-class mode in your configuration.",
method.getName(), method.getDeclaringClass().getSimpleName()));
} }
/**
* A callback interface for metadata lookup on a given method.
* @param <T> the type of metadata returned
*/
@FunctionalInterface
public interface MetadataLookup<T> {
/**
* Perform a lookup on the given method and return associated metadata, if any.
* @param method the method to inspect
* @return non-null metadata to be associated with a method if there is a match,
* or {@code null} for no match
*/
@Nullable T inspect(Method method);
}
}