graphql.schema.PropertyDataFetcher Maven / Gradle / Ivy
package graphql.schema;
import graphql.Assert;
import graphql.GraphQLException;
import graphql.PublicApi;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.Function;
import static graphql.Scalars.GraphQLBoolean;
import static graphql.schema.GraphQLTypeUtil.isNonNull;
import static graphql.schema.GraphQLTypeUtil.unwrapOne;
/**
* This is the default data fetcher used in graphql-java. It will examine
* maps and POJO java beans for values that match the desired name, typically the field name
* or it will use a provided function to obtain values.
* maps and POJO java beans for values that match the desired name.
*
* It uses the following strategies
*
* - If the source is null, return null
* - If the source is a Map, return map.get(propertyName)
* - If a function is provided, it is used
* - Find a public JavaBean getter method named `propertyName`
* - Find any getter method named `propertyName` and call method.setAccessible(true)
* - Find a public field named `propertyName`
* - Find any field named `propertyName` and call field.setAccessible(true)
* - If this cant find anything, then null is returned
*
*
* You can write your own data fetchers to get data from some other backing system
* if you need highly customised behaviour.
*
* @see graphql.schema.DataFetcher
*/
@PublicApi
public class PropertyDataFetcher implements DataFetcher {
private final String propertyName;
private final Function function;
/**
* This constructor will use the property name and examine the {@link DataFetchingEnvironment#getSource()}
* object for a getter method or field with that name.
*
* @param propertyName the name of the property to retrieve
*/
public PropertyDataFetcher(String propertyName) {
this.propertyName = Assert.assertNotNull(propertyName);
this.function = null;
}
@SuppressWarnings("unchecked")
private PropertyDataFetcher(Function function) {
this.function = (Function) Assert.assertNotNull(function);
this.propertyName = null;
}
/**
* Returns a data fetcher that will use the property name to examine the {@link DataFetchingEnvironment#getSource()} object
* for a getter method or field with that name, or if its a map, it will look up a value using
* property name as a key.
*
* For example :
*
* {@code
*
* DataFetcher functionDataFetcher = fetching("pojoPropertyName");
*
* }
*
*
* @param propertyName the name of the property to retrieve
* @param the type of result
*
* @return a new PropertyDataFetcher using the provided function as its source of values
*/
public static PropertyDataFetcher fetching(String propertyName) {
return new PropertyDataFetcher<>(propertyName);
}
/**
* Returns a data fetcher that will present the {@link DataFetchingEnvironment#getSource()} object to the supplied
* function to obtain a value, which allows you to use Java 8 method references say obtain values in a
* more type safe way.
*
* For example :
*
* {@code
*
* DataFetcher functionDataFetcher = fetching(Thing::getId);
*
* }
*
*
* @param function the function to use to obtain a value from the source object
* @param the type of the source object
* @param the type of result
*
* @return a new PropertyDataFetcher using the provided function as its source of values
*/
public static PropertyDataFetcher fetching(Function function) {
return new PropertyDataFetcher<>(function);
}
/**
* @return the property that this is fetching for
*/
public String getPropertyName() {
return propertyName;
}
@SuppressWarnings("unchecked")
@Override
public T get(DataFetchingEnvironment environment) {
Object source = environment.getSource();
if (source == null) {
return null;
}
if (function != null) {
return (T) function.apply(source);
}
if (source instanceof Map) {
return (T) ((Map) source).get(propertyName);
}
return (T) getPropertyViaGetter(source, environment.getFieldType());
}
private Object getPropertyViaGetter(Object object, GraphQLOutputType outputType) {
try {
return getPropertyViaGetterMethod(object, outputType, this::findPubliclyAccessibleMethod);
} catch (NoSuchMethodException ignored) {
try {
return getPropertyViaGetterMethod(object, outputType, this::findViaSetAccessible);
} catch (NoSuchMethodException ignored2) {
return getPropertyViaFieldAccess(object);
}
}
}
@FunctionalInterface
private interface MethodFinder {
Method apply(Class aClass, String s) throws NoSuchMethodException;
}
private Object getPropertyViaGetterMethod(Object object, GraphQLOutputType outputType, MethodFinder methodFinder) throws NoSuchMethodException {
if (isBooleanProperty(outputType)) {
try {
return getPropertyViaGetterUsingPrefix(object, "is", methodFinder);
} catch (NoSuchMethodException e) {
return getPropertyViaGetterUsingPrefix(object, "get", methodFinder);
}
} else {
return getPropertyViaGetterUsingPrefix(object, "get", methodFinder);
}
}
private Object getPropertyViaGetterUsingPrefix(Object object, String prefix, MethodFinder methodFinder) throws NoSuchMethodException {
String getterName = prefix + propertyName.substring(0, 1).toUpperCase() + propertyName.substring(1);
try {
Method method = methodFinder.apply(object.getClass(), getterName);
return method.invoke(object);
} catch (IllegalAccessException | InvocationTargetException e) {
throw new GraphQLException(e);
}
}
@SuppressWarnings("SimplifiableIfStatement")
private boolean isBooleanProperty(GraphQLOutputType outputType) {
if (outputType == GraphQLBoolean) {
return true;
}
if (isNonNull(outputType)) {
return unwrapOne(outputType) == GraphQLBoolean;
}
return false;
}
private static final ConcurrentMap METHOD_CACHE = new ConcurrentHashMap<>();
private static final ConcurrentMap FIELD_CACHE = new ConcurrentHashMap<>();
/**
* PropertyDataFetcher caches the methods and fields that map from a class to a property for runtime performance reasons.
*
* However during development you might be using an assistance tool like JRebel to allow you to tweak your code base and this
* caching may interfere with this. So you can call this method to clear the cache. A JRebel plugin could
* be developed to do just that.
*/
@SuppressWarnings("unused")
public static void clearReflectionCache() {
METHOD_CACHE.clear();
FIELD_CACHE.clear();
}
private String mkKey(Class clazz, String propertyName) {
return clazz.getName() + "__" + propertyName;
}
// by not filling out the stack trace, we gain speed when using the exception as flow control
private static class FastNoSuchMethodException extends NoSuchMethodException {
public FastNoSuchMethodException(String methodName) {
super(methodName);
}
@Override
public synchronized Throwable fillInStackTrace() {
return this;
}
}
/**
* Invoking public methods on package-protected classes via reflection
* causes exceptions. This method searches a class's hierarchy for
* public visibility parent classes with the desired getter. This
* particular case is required to support AutoValue style data classes,
* which have abstract public interfaces implemented by package-protected
* (generated) subclasses.
*/
@SuppressWarnings("unchecked")
private Method findPubliclyAccessibleMethod(Class root, String methodName) throws NoSuchMethodException {
Class currentClass = root;
while (currentClass != null) {
String key = mkKey(currentClass, propertyName);
Method method = METHOD_CACHE.get(key);
if (method != null) {
return method;
}
if (Modifier.isPublic(currentClass.getModifiers())) {
method = currentClass.getMethod(methodName);
if (Modifier.isPublic(method.getModifiers())) {
METHOD_CACHE.putIfAbsent(key, method);
return method;
}
}
currentClass = currentClass.getSuperclass();
}
return root.getMethod(methodName);
}
private Method findViaSetAccessible(Class aClass, String methodName) throws NoSuchMethodException {
String key = mkKey(aClass, propertyName);
Method method = METHOD_CACHE.get(key);
if (method != null) {
return method;
}
Method[] declaredMethods = aClass.getDeclaredMethods();
Optional m = Arrays.stream(declaredMethods)
.filter(mth -> methodName.equals(mth.getName()))
.findFirst();
if (m.isPresent()) {
try {
// few JVMs actually enforce this but it might happen
method = m.get();
method.setAccessible(true);
METHOD_CACHE.putIfAbsent(key, method);
return method;
} catch (SecurityException ignored) {
}
}
throw new FastNoSuchMethodException(methodName);
}
private Object getPropertyViaFieldAccess(Object object) {
Class aClass = object.getClass();
String key = mkKey(aClass, propertyName);
try {
Field field = FIELD_CACHE.get(key);
if (field == null) {
field = aClass.getField(propertyName);
FIELD_CACHE.putIfAbsent(key, field);
}
return field.get(object);
} catch (NoSuchFieldException e) {
// if not public fields then try via setAccessible
try {
Field field = aClass.getDeclaredField(propertyName);
field.setAccessible(true);
FIELD_CACHE.putIfAbsent(key, field);
return field.get(object);
} catch (SecurityException | NoSuchFieldException ignored2) {
return null;
} catch (IllegalAccessException e1) {
throw new GraphQLException(e);
}
} catch (IllegalAccessException e) {
throw new GraphQLException(e);
}
}
}
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