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Rule-based UI form validation library for Android
/*
* Copyright (C) 2014 Mobs & Geeks
*
* 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.mobsandgeeks.saripaar;
import android.view.View;
import com.mobsandgeeks.saripaar.adapter.ViewDataAdapter;
import com.mobsandgeeks.saripaar.annotation.ValidateUsing;
import com.mobsandgeeks.saripaar.exception.SaripaarViolationException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
/**
* Contains reflection methods that are helpful for introspection and retrieval of frequently used
* methods and attributes.
*
* @author Ragunath Jawahar {@literal }
* @since 2.0
*/
final class Reflector {
/**
* Retrieves the attribute method of the given {@link java.lang.annotation.Annotation}.
*
* @param annotationType The {@link java.lang.annotation.Annotation}
* {@link java.lang.Class} to check.
* @param attributeName Attribute name.
*
* @return The {@link java.lang.reflect.Method} if the attribute is present,
* null otherwise.
*/
public static Method getAttributeMethod(final Class annotationType,
final String attributeName) {
Method attributeMethod = null;
try {
attributeMethod = annotationType.getMethod(attributeName);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
return attributeMethod;
}
/**
* Retrieve an attribute value from an {@link java.lang.annotation.Annotation}.
*
* @param annotation An {@link java.lang.annotation.Annotation} instance.
* @param attributeName Attribute name.
* @param attributeDataType {@link java.lang.Class} representing the attribute data type.
* @param Attribute value type.
*
* @return The attribute value.
*/
@SuppressWarnings("unchecked")
public static T getAttributeValue(final Annotation annotation, final String attributeName,
final Class attributeDataType) {
T attributeValue = null;
Class annotationType = annotation.annotationType();
Method attributeMethod = getAttributeMethod(annotationType, attributeName);
if (attributeMethod == null) {
String message = String.format("Cannot find attribute '%s' in annotation '%s'.",
attributeName, annotationType.getName());
throw new IllegalStateException(message);
} else {
try {
Object result = attributeMethod.invoke(annotation);
attributeValue = attributeDataType.isPrimitive()
? (T) result
: attributeDataType.cast(result);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
return attributeValue;
}
/**
* Checks if an annotation was annotated with the given annotation.
*
* @param inspected The {@link java.lang.annotation.Annotation} to be checked.
* @param expected The {@link java.lang.annotation.Annotation} that we are looking for.
*
* @return true if the annotation is present, false otherwise.
*/
public static boolean isAnnotated(final Class inspected,
final Class expected) {
boolean isAnnotated = false;
Annotation[] declaredAnnotations = inspected.getDeclaredAnnotations();
for (Annotation declaredAnnotation : declaredAnnotations) {
isAnnotated = expected.equals(declaredAnnotation.annotationType());
if (isAnnotated) {
break;
}
}
return isAnnotated;
}
/**
* Finds and returns the correct
* {@link com.mobsandgeeks.saripaar.adapter.ViewDataAdapter#getData(android.view.View)}
* {@link java.lang.reflect.Method}.
*
* @param dataAdapterType The {@link com.mobsandgeeks.saripaar.adapter.ViewDataAdapter}
* class whose {@code getData(View)} method is required.
*
* @return The correct {@code getData(View)} method.
*/
public static Method findGetDataMethod(final Class dataAdapterType) {
Method getDataMethod = null;
Method[] declaredMethods = dataAdapterType.getDeclaredMethods();
for (Method method : declaredMethods) {
boolean methodNameIsGetData = "getData".equals(method.getName());
if (methodNameIsGetData) {
// If we don't declare a throws clause in the method signature, the compiler
// creates an auto-generated volatile method with the java.lang.Object return type.
int modifiers = method.getModifiers();
boolean nonVolatile = !Modifier.isVolatile(modifiers);
// Single 'View' parameter
Class[] parameterTypes = method.getParameterTypes();
boolean hasSingleViewParameter = parameterTypes.length == 1
&& View.class.isAssignableFrom(parameterTypes[0]);
if (nonVolatile && hasSingleViewParameter) {
getDataMethod = method;
break;
}
}
}
return getDataMethod;
}
/**
* Instantiates a {@link AnnotationRule} object for the given type.
*
* @param ruleType The {@link AnnotationRule} class to be instantiated.
* @param ruleAnnotation The rule {@link java.lang.annotation.Annotation} associated with
* the {@link AnnotationRule}.
*
* @return The instantiated {@link AnnotationRule} object.
*
* @throws SaripaarViolationException if {@link AnnotationRule} does not
* have a single-argument constructor that accepts a rule
* {@link java.lang.annotation.Annotation} instance.
*/
public static AnnotationRule instantiateRule(final Class ruleType,
final Annotation ruleAnnotation, final ValidationContext validationContext)
throws SaripaarViolationException {
AnnotationRule rule = null;
try {
if (ContextualAnnotationRule.class.isAssignableFrom(ruleType)) {
Constructor constructor = ruleType.getDeclaredConstructor(
ValidationContext.class, ruleAnnotation.annotationType());
constructor.setAccessible(true);
rule = (AnnotationRule) constructor.newInstance(validationContext, ruleAnnotation);
} else if (AnnotationRule.class.isAssignableFrom(ruleType)) {
Constructor constructor = ruleType.getDeclaredConstructor(
ruleAnnotation.annotationType());
constructor.setAccessible(true);
rule = (AnnotationRule) constructor.newInstance(ruleAnnotation);
}
} catch (NoSuchMethodException e) {
String message = getMissingConstructorErrorMessage(ruleType,
ruleAnnotation.annotationType());
throw new SaripaarViolationException(message);
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return rule;
}
/**
* Method finds the data type of the {@link AnnotationRule} that is tied up to the given rule
* annotation.
*
* @param ruleAnnotation Rule {@link java.lang.annotation.Annotation}.
*
* @return The expected data type for the
* {@link com.mobsandgeeks.saripaar.adapter.ViewDataAdapter}s.
*/
public static Class getRuleDataType(final Annotation ruleAnnotation) {
ValidateUsing validateUsing = getValidateUsingAnnotation(ruleAnnotation.annotationType());
return getRuleDataType(validateUsing);
}
/**
* Method finds the data type of the {@link AnnotationRule} that is tied up to the given rule
* annotation.
*
* @param validateUsing The {@link com.mobsandgeeks.saripaar.annotation.ValidateUsing}
* instance.
*
* @return The expected data type for the
* {@link com.mobsandgeeks.saripaar.adapter.ViewDataAdapter}s.
*/
public static Class getRuleDataType(final ValidateUsing validateUsing) {
Class rule = validateUsing.value();
Method[] methods = rule.getDeclaredMethods();
return getRuleTypeFromIsValidMethod(rule, methods);
}
/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Private Methods
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
private static ValidateUsing getValidateUsingAnnotation(
final Class annotationType) {
ValidateUsing validateUsing = null;
Annotation[] declaredAnnotations = annotationType.getDeclaredAnnotations();
for (Annotation annotation : declaredAnnotations) {
if (ValidateUsing.class.equals(annotation.annotationType())) {
validateUsing = (ValidateUsing) annotation;
break;
}
}
return validateUsing;
}
private static String getMissingConstructorErrorMessage(
final Class ruleType,
final Class annotationType) {
String message = null;
if (ContextualAnnotationRule.class.isAssignableFrom(ruleType)) {
message = String.format("A constructor accepting a '%s' and a '%s' is required for %s.",
ValidationContext.class, annotationType.getName(),
ruleType.getClass().getName());
} else if (AnnotationRule.class.isAssignableFrom(ruleType)) {
message = String.format(
"'%s' should have a single-argument constructor that accepts a '%s' instance.",
ruleType.getName(), annotationType.getName());
}
return message;
}
private static Class getRuleTypeFromIsValidMethod(final Class rule,
final Method[] methods) {
Class returnType = null;
for (Method method : methods) {
Class[] parameterTypes = method.getParameterTypes();
if (matchesIsValidMethodSignature(method, parameterTypes)) {
// This will be null, if there are no matching methods
// in the class with a similar signature.
if (returnType != null) {
String message = String.format(
"Found duplicate 'boolean isValid(T)' method signature in '%s'.",
rule.getName());
throw new SaripaarViolationException(message);
}
returnType = parameterTypes[0];
}
}
return returnType;
}
private static boolean matchesIsValidMethodSignature(final Method method,
final Class[] parameterTypes) {
int modifiers = method.getModifiers();
boolean isPublic = Modifier.isPublic(modifiers);
boolean nonVolatile = !Modifier.isVolatile(modifiers);
boolean returnsBoolean = Boolean.TYPE.equals(method.getReturnType());
boolean matchesMethodName = "isValid".equals(method.getName());
boolean hasSingleParameter = parameterTypes.length == 1;
return isPublic && nonVolatile && returnsBoolean && matchesMethodName && hasSingleParameter;
}
private Reflector() {
}
}