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EasyMock provides an easy way to create Mock Objects for interfaces and classes generating them on the fly
/**
* Copyright 2001-2015 the original author or authors.
*
* 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 org.easymock.internal;
import org.easymock.EasyMock;
import java.io.*;
import java.lang.reflect.*;
/**
* Default class instantiator that is pretty limited. It just hope that the
* mocked class has a public empty constructor.
*
* @author Henri Tremblay
*/
public class DefaultClassInstantiator implements IClassInstantiator {
private static final Class[] EMPTY = new Class[0];
/**
* Try to instantiate a class without using a special constructor. See
* documentation for the algorithm.
*
* @param c
* Class to instantiate
*/
public Object newInstance(Class c) throws InstantiationException {
if (isSerializable(c)) {
try {
return readObject(getSerializedBytes(c));
// ///CLOVER:OFF
} catch (IOException e) {
throw new RuntimeException("Failed to instantiate " + c.getName() + "'s mock: ", e);
} catch (ClassNotFoundException e) {
throw new RuntimeException("Failed to instantiate " + c.getName() + "'s mock: ", e);
}
// ///CLOVER:ON
}
Constructor constructor = getConstructorToUse(c);
Object[] params = getArgsForTypes(constructor.getParameterTypes());
try {
return constructor.newInstance(params);
// ///CLOVER:OFF
} catch (IllegalArgumentException e) {
throw new RuntimeException("Failed to instantiate " + c.getName() + "'s mock: ", e);
} catch (IllegalAccessException e) {
throw new RuntimeException("Failed to instantiate " + c.getName() + "'s mock: ", e);
// ///CLOVER:ON
} catch (InvocationTargetException e) {
throw new RuntimeException("Failed to instantiate " + c.getName() + "'s mock: ", e);
}
}
/**
* Tells if the provided class is serializable
*
* @param clazz
* Class to check
* @return If the class is serializable
*/
private boolean isSerializable(Class clazz) {
return Serializable.class.isAssignableFrom(clazz);
}
/**
* Return the constructor considered the best to use with this class.
* Algorithm is: No args constructor and then first constructor defined in
* the class
*
* @param clazz
* Class in which constructor is searched
* @return Constructor to use
*/
public Constructor getConstructorToUse(Class clazz) {
// First try to use the empty constructor
try {
return clazz.getConstructor(EMPTY);
} catch (NoSuchMethodException e) {
// If it fails just use the first one
if (clazz.getConstructors().length == 0) {
throw new IllegalArgumentException("No visible constructors in class " + clazz.getName());
}
return clazz.getConstructors()[0];
}
}
/**
* Get some default instances of provided classes
*
* @param methodTypes
* Classes to instantiate
* @return Instances of methodTypes in order
* @throws InstantiationException Thrown if the class instantiation fails
*/
public Object[] getArgsForTypes(Class[] methodTypes) throws InstantiationException {
Object[] methodArgs = new Object[methodTypes.length];
for (int i = 0; i < methodTypes.length; i++) {
if (methodTypes[i].isPrimitive()) {
// Return a nice wrapped primitive type
methodArgs[i] = RecordState.emptyReturnValueFor(methodTypes[i]);
// ///CLOVER:OFF TODO: Remove when we manage to fix the ignored tests
} else if (Modifier.isFinal(methodTypes[i].getModifiers())) {
// Instantiate the class using the best constructor we can find
// (because it's not
// possible to mock a final class)
methodArgs[i] = newInstance(methodTypes[i]);
// ///CLOVER:ON
} else {
// For all classes and interfaces, just return a nice mock
Object mock = EasyMock.createNiceMock(methodTypes[i]);
EasyMock.replay(mock);
methodArgs[i] = mock;
}
}
return methodArgs;
}
private static byte[] getSerializedBytes(Class clazz) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream data = new DataOutputStream(baos);
try {
data.writeShort(ObjectStreamConstants.STREAM_MAGIC);
data.writeShort(ObjectStreamConstants.STREAM_VERSION);
data.writeByte(ObjectStreamConstants.TC_OBJECT);
data.writeByte(ObjectStreamConstants.TC_CLASSDESC);
data.writeUTF(clazz.getName());
Long suid = getSerializableUID(clazz);
data.writeLong(suid.longValue());
data.writeByte(2); // classDescFlags (2 = Serializable)
data.writeShort(0); // field count
data.writeByte(ObjectStreamConstants.TC_ENDBLOCKDATA);
data.writeByte(ObjectStreamConstants.TC_NULL);
}
finally {
data.close();
}
return baos.toByteArray();
}
private static Long getSerializableUID(Class clazz) {
try {
Field f = clazz.getDeclaredField("serialVersionUID");
int mask = Modifier.STATIC | Modifier.FINAL;
if ((f.getModifiers() & mask) == mask) {
f.setAccessible(true);
return Long.valueOf(f.getLong(null));
}
} catch (NoSuchFieldException e) {
// It's not there, compute it then
} catch (IllegalAccessException e) {
// ///CLOVER:OFF
throw new RuntimeException("Should have been able to get serialVersionUID since it's there");
// ///CLOVER:ON
}
// ///CLOVER:OFF
return callLongMethod(clazz,
ClassInstantiatorFactory.is1_3Specifications() ? "computeSerialVersionUID"
: "computeDefaultSUID");
// ///CLOVER:ON
}
private static Long callLongMethod(Class clazz, String methodName) {
Method method;
// ///CLOVER:OFF
try {
method = ObjectStreamClass.class.getDeclaredMethod(methodName, Class.class);
} catch (NoSuchMethodException e) {
throw new InternalError("ObjectStreamClass." + methodName + " seems to have vanished");
}
boolean accessible = method.isAccessible();
method.setAccessible(true);
Long suid;
try {
suid = (Long) method.invoke(null, clazz);
} catch (IllegalAccessException e) {
throw new InternalError("ObjectStreamClass." + methodName + " should have been accessible");
} catch (InvocationTargetException e) {
throw new InternalError("ObjectStreamClass." + methodName + " failled to be called: "
+ e.getMessage());
}
method.setAccessible(accessible);
// ///CLOVER:ON
return suid;
}
private static Object readObject(byte[] bytes) throws IOException, ClassNotFoundException {
ObjectInputStream in = new ObjectInputStream(new ByteArrayInputStream(bytes));
try {
return in.readObject();
}
finally {
in.close();
}
}
}