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/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.api.server.spi;
import com.google.common.base.Preconditions;
import com.google.common.reflect.TypeToken;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
/**
* A class which takes care to resolved any parameterized types for endpoints. That way we
* can support inheritance from generic base classes without needing to override and specialize
* the method when it has a sensible default.
*/
public class EndpointMethod {
/**
* Adapter class to compare {@code EndpointMethod} instances based on their Java method signature
* rather than the actual method implementation. Comparisons are based on resolved types.
*
* This is a pure adapter class containing no state of its own, relying entirely on the state
* of the owning {@code EndpointMethod} object. All access to the owning object is made through
* qualified this calls to make dependencies as clear as possible.
*/
public class ResolvedSignature {
public String getSignatureName() {
return EndpointMethod.this.getMethod().getName();
}
public Class[] getSignatureParameterClasses() {
return EndpointMethod.this.getParameterClasses();
}
@Override
public boolean equals(Object o) {
if (o == this) {
return true;
}
if (!(o instanceof ResolvedSignature)) {
return false;
}
ResolvedSignature signature = (ResolvedSignature) o;
return (getSignatureName().equals(signature.getSignatureName()) &&
Arrays.equals(getSignatureParameterClasses(), signature.getSignatureParameterClasses()));
}
@Override
public int hashCode() {
return Objects.hash(getSignatureName(), Arrays.hashCode(getSignatureParameterClasses()));
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder(getSignatureName()).append("(");
for (Class clazz : getSignatureParameterClasses()) {
builder.append(clazz.toString()).append(", ");
}
builder.delete(builder.length() - 2, builder.length());
builder.append(")");
return builder.toString();
}
}
/**
* The endpoint class.
*/
private final Class endpointClass;
/**
* The underlying method.
*/
private final Method method;
/**
* A {@code TypeToken} for the method's declaring class. Used to resolve types.
*/
private final TypeToken typeToken;
private final ResolvedSignature resolvedMethodSignature;
private List parameterNames;
private EndpointMethod(Class endpointClass, Method method, TypeToken token) {
this.endpointClass = endpointClass;
this.method = method;
this.resolvedMethodSignature = new ResolvedSignature();
this.typeToken = token;
}
private Type resolve(Type type) {
return typeToken.resolveType(type).getType();
}
private Type[] resolve(Type[] types) {
Type[] resolved = new Type[types.length];
for (int i = 0; i < types.length; ++i) {
resolved[i] = resolve(types[i]);
}
return resolved;
}
private static Class[] resolveClasses(Type[] types) {
Class[] resolved = new Class[types.length];
for (int i = 0; i < types.length; ++i) {
resolved[i] = getClassFromType(types[i]);
}
return resolved;
}
/**
* Returns the class associated with {@code type}. If this is a parameterized type or generic
* array, then its raw or component type, respectively, will be returned. Null is returned
* if {@code type} is not implemented by a {@code Class}, {@code ParameterizedType}, or
* {@code GenericArrayType} object.
*/
public static Class getClassFromType(Type type) {
if (type instanceof Class) {
return (Class) type;
} else if (type instanceof ParameterizedType) {
return getClassFromType(((ParameterizedType) type).getRawType());
} else if (type instanceof GenericArrayType) {
Type componentType = ((GenericArrayType) type).getGenericComponentType();
Class componentClass = getClassFromType(componentType);
if (componentClass != null) {
return Array.newInstance(componentClass, 0).getClass();
}
}
return null;
}
/**
* Returns the endpoint class.
*/
public Class getEndpointClass() {
return endpointClass;
}
/**
* Returns the underlying method object.
*/
public Method getMethod() {
return method;
}
/**
* Returns the return type of the method.
*/
public Type getReturnType() {
return resolve(method.getGenericReturnType());
}
/**
* Returns the parameter types of the method.
*/
public Type[] getParameterTypes() {
return resolve(method.getGenericParameterTypes());
}
/**
* Returns the parameter classes of the method.
*/
public Class[] getParameterClasses() {
return resolveClasses(getParameterTypes());
}
private void validateNoWildcards(Type[] types) {
for (Type type : types) {
Type resolved = typeToken.resolveType(type).getType();
if (resolved instanceof ParameterizedType) {
validateNoWildcards(((ParameterizedType) resolved).getActualTypeArguments());
} else if (resolved instanceof WildcardType) {
throw new IllegalArgumentException(
// TODO: Figure out a more useful error message. Maybe try to provide the
// location of the wildcard instead of just its name ('T' is not the most useful info).
String.format("Wildcard type %s not supported", resolved));
}
}
}
/**
* Creates an {@link EndpointMethod} using type information from the given {@link TypeToken}.
*
* @param method Must not have wildcard types (all generic types must be resolvable to a concrete
* type using the given {@link TypeToken}).
* @param token A token for the method's declaring class.
*/
public static EndpointMethod create(
Class endpointClass, Method method, TypeToken token) {
Preconditions.checkNotNull(endpointClass, "endpointClass");
Preconditions.checkNotNull(method, "method");
Preconditions.checkArgument(method.getDeclaringClass().isAssignableFrom(endpointClass),
"Method '%s' does belong to interface of class '%s'", method, endpointClass);
Preconditions.checkArgument(method.getDeclaringClass().equals(token.getRawType()),
"Token must be of the method's declaring class '%s'.", method.getDeclaringClass());
EndpointMethod endpointMethod = new EndpointMethod(endpointClass, method, token);
endpointMethod.validateNoWildcards(new Type[] { endpointMethod.getReturnType() });
endpointMethod.validateNoWildcards(endpointMethod.getParameterTypes());
return endpointMethod;
}
/**
* Creates an {@link EndpointMethod} using type information directly available from the method's
* declaring class.
*
* @param method Must not have wildcard types (all generic types must be resolvable to a concrete
* type using type information from the method's declaring class).
*/
public static EndpointMethod create(Class endpointClass, Method method) {
return create(endpointClass, method, TypeToken.of(method.getDeclaringClass()));
}
public ResolvedSignature getResolvedMethodSignature() {
return resolvedMethodSignature;
}
@Override
public boolean equals(Object o) {
if (o == this) {
return true;
}
if (!(o instanceof EndpointMethod)) {
return false;
}
EndpointMethod m = (EndpointMethod) o;
return this.getMethod().equals(m.getMethod());
}
@Override
public String toString() {
return new StringBuilder("Method: ").append(getMethod().toString())
.append(", Resolved Return Type: ").append(getReturnType())
.append(", Resolved Parameter Types: ").append(Arrays.toString(getParameterTypes()))
.toString();
}
@Override
public int hashCode() {
return Objects.hash(getMethod());
}
public List getParameterNames() {
List names = parameterNames;
return names == null ? null : new ArrayList(names);
}
public void setParameterNames(List parameterNames) {
this.parameterNames = parameterNames;
}
}