gmbh.dtap.geojson.serializer.ClassUtils Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of geojson-serializer Show documentation
Show all versions of geojson-serializer Show documentation
A library with a JsonSerializer and a set of annotations to serialize any PoJo as GeoJSON.
/*
* Copyright 2019 DTAP GmbH
*
* 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 gmbh.dtap.geojson.serializer;
import gmbh.dtap.geojson.annotation.GeoJsonGeometry;
import org.apache.commons.lang3.reflect.FieldUtils;
import org.locationtech.jts.geom.Geometry;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import static org.apache.commons.lang3.StringUtils.removeStart;
import static org.apache.commons.lang3.StringUtils.uncapitalize;
/**
* Utility class for the serializers.
*
* @see GeoJsonSerializer
* @see FeatureSerializer
* @see FeatureCollectionSerializer
* @since 0.2.0
*/
class ClassUtils {
private ClassUtils() {
// static usage only
}
/**
* Scans the class of the object for one annotation of type {@link GeoJsonGeometry}.
* If present, the value of the annotated getter or field will be returned if it's an
* implementation of {@link Geometry}.
*
* @param object the object of which the class should be scanned
* @return the geometry object, or null if annotation is not present
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static Geometry findGeometry(Object object) {
Member member = findOne(object, GeoJsonGeometry.class);
if (member != null) {
Object value = getValue(object, member, Geometry.class);
return Geometry.class.cast(value);
}
return null;
}
/**
* Scans the class of the object for one annotation of a given type.
*
* @param object the object of which the class should be scanned
* @param annotationClass the annotation to scan for
* @return the annotated field or getter, or null if not present
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static Member findOne(Object object, Class annotationClass) {
List members = scanFor(object, annotationClass);
if (members.isEmpty()) {
return null;
} else {
if (members.size() > 1) {
throw new GeoJsonSerializerException("annotation " + annotationClass + " found more than once in object " + object);
}
return members.get(0);
}
}
/**
* Scans the class of the object for all annotations of a given type.
*
* @param object the object of which the class should be scanned
* @param annotationClass the annotation to scan for
* @return the annotated fields and getters, maybe empty but never null
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static List scanFor(Object object, Class annotationClass) {
List members = new ArrayList<>();
for (Field field : object.getClass().getDeclaredFields()) {
if (field.isAnnotationPresent(annotationClass)) {
members.add(field);
}
}
for (PropertyDescriptor propertyDescriptor : getBeanInfo(object).getPropertyDescriptors()) {
Method method = propertyDescriptor.getReadMethod();
if (method.isAnnotationPresent(annotationClass)) {
members.add(method);
}
}
return members;
}
/**
* Returns the name of the given field or getter.
*
* @param member the field or getter
* @return the field name as is, or the getter name without get and uncapitalized
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static String getName(Member member) {
if (member instanceof Field) {
return member.getName();
} else if (member instanceof Method) {
return uncapitalize(removeStart(member.getName(), "get"));
} else {
throw new IllegalStateException("unexpected member: " + member);
}
}
/**
* Returns the value of a field or getter the returned value of a getter.
*
* @param object the object of which the value should be returned
* @param member the field getter to invoke
* @param expectedClass the expected type of value
* @param the class of the expected type
* @return the value, may be null
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static T getValue(Object object, Member member, Class expectedClass) {
if (member instanceof Field) {
return getValueFromField(object, (Field) member, expectedClass);
} else if (member instanceof Method) {
return getValueFromMethod(object, (Method) member, expectedClass);
} else {
throw new IllegalStateException("unexpected member: " + member);
}
}
/**
* Returns the value of a field.
*
* @param object the object of which the value should be returned
* @param field the field to get the value from
* @param expectedClass the expected type of value
* @param the class of the expected type
* @return the value, may be null
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static T getValueFromField(Object object, Field field, Class expectedClass) {
Object value;
try {
value = FieldUtils.readField(field, object, true);
} catch (Exception e) {
throw new GeoJsonSerializerException("value from Field failed: object=" + object + ", field=" + field, e);
}
if (value != null && !expectedClass.isInstance(value)) {
throw new GeoJsonSerializerException("value from Field is not of expected type: object=" + object + ", field=" + field + ", expectedType=" + expectedClass);
}
return expectedClass.cast(value);
}
/**
* Returns the value of a getter.
*
* @param object the object of which the value should be returned
* @param method the getter to invoke
* @param expectedClass the expected type of value
* @param the class of the expected type
* @return the value, may be null
* @throws GeoJsonSerializerException on any error
* @since 0.2.0
*/
static T getValueFromMethod(Object object, Method method, Class expectedClass) {
Object value;
try {
value = method.invoke(object);
} catch (Exception e) {
throw new GeoJsonSerializerException("value from Method failed: object=" + object + ", method=" + method, e);
}
if (!expectedClass.isInstance(value)) {
throw new GeoJsonSerializerException("value from Method is not of expected type: object=" + object + ", method=" + method + ", expectedType=" + expectedClass);
}
return expectedClass.cast(value);
}
private static BeanInfo getBeanInfo(Object object) {
try {
return Introspector.getBeanInfo(object.getClass());
} catch (IntrospectionException e) {
throw new GeoJsonSerializerException("introspection of object failed: " + object, e);
}
}
}