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SAXDecoder.java
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169 lines (147 loc) · 6.27 KB
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/**
* Copyright 2012-2018 The Feign 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 feign.sax;
import org.xml.sax.ContentHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.Type;
import java.util.LinkedHashMap;
import java.util.Map;
import feign.Response;
import feign.Util;
import feign.codec.DecodeException;
import feign.codec.Decoder;
import static feign.Util.checkNotNull;
import static feign.Util.checkState;
import static feign.Util.ensureClosed;
import static feign.Util.resolveLastTypeParameter;
/**
* Decodes responses using SAX, which is supported both in normal JVM environments, as well Android.
* <br> <h4>Basic example with with Feign.Builder</h4> <br>
* <pre>
* api = Feign.builder()
* .decoder(SAXDecoder.builder()
* .registerContentHandler(ContentHandlerForFoo.class)
* .registerContentHandler(ContentHandlerForBar.class)
* .build())
* .target(MyApi.class, "http://api");
* </pre>
*/
public class SAXDecoder implements Decoder {
private final Map<Type, ContentHandlerWithResult.Factory<?>> handlerFactories;
private SAXDecoder(Map<Type, ContentHandlerWithResult.Factory<?>> handlerFactories) {
this.handlerFactories = handlerFactories;
}
public static Builder builder() {
return new Builder();
}
@Override
public Object decode(Response response, Type type) throws IOException, DecodeException {
if (response.status() == 404) return Util.emptyValueOf(type);
if (response.body() == null) return null;
ContentHandlerWithResult.Factory<?> handlerFactory = handlerFactories.get(type);
checkState(handlerFactory != null, "type %s not in configured handlers %s", type,
handlerFactories.keySet());
ContentHandlerWithResult<?> handler = handlerFactory.create();
try {
XMLReader xmlReader = XMLReaderFactory.createXMLReader();
xmlReader.setFeature("http://xml.org/sax/features/namespaces", false);
xmlReader.setFeature("http://xml.org/sax/features/validation", false);
/* Explicitly control sax configuration to prevent XXE attacks */
xmlReader.setFeature("http://xml.org/sax/features/external-general-entities", false);
xmlReader.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
xmlReader.setFeature("http://apache.org/xml/features/disallow-doctype-decl", false);
xmlReader.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
xmlReader.setContentHandler(handler);
InputStream inputStream = response.body().asInputStream();
try {
xmlReader.parse(new InputSource(inputStream));
} finally {
ensureClosed(inputStream);
}
return handler.result();
} catch (SAXException e) {
throw new DecodeException(e.getMessage(), e);
}
}
/**
* Implementations are not intended to be shared across requests.
*/
public interface ContentHandlerWithResult<T> extends ContentHandler {
/**
* expected to be set following a call to {@link XMLReader#parse(InputSource)}
*/
T result();
public interface Factory<T> {
ContentHandlerWithResult<T> create();
}
}
public static class Builder {
private final Map<Type, ContentHandlerWithResult.Factory<?>> handlerFactories =
new LinkedHashMap<Type, ContentHandlerWithResult.Factory<?>>();
/**
* Will call {@link Constructor#newInstance(Object...)} on {@code handlerClass} for each content
* stream. <p/> <h3>Note</h3> <br/> While this is costly vs {@code new}, it may not affect real
* performance due to the high cost of reading streams.
*
* @throws IllegalArgumentException if there's no no-arg constructor on {@code handlerClass}.
*/
public <T extends ContentHandlerWithResult<?>> Builder registerContentHandler(
Class<T> handlerClass) {
Type
type =
resolveLastTypeParameter(checkNotNull(handlerClass, "handlerClass"),
ContentHandlerWithResult.class);
return registerContentHandler(type,
new NewInstanceContentHandlerWithResultFactory(handlerClass));
}
/**
* Will call {@link ContentHandlerWithResult.Factory#create()} on {@code handler} for each
* content stream. The {@code handler} is expected to have a generic parameter of {@code type}.
*/
public Builder registerContentHandler(Type type, ContentHandlerWithResult.Factory<?> handler) {
this.handlerFactories.put(checkNotNull(type, "type"), checkNotNull(handler, "handler"));
return this;
}
public SAXDecoder build() {
return new SAXDecoder(handlerFactories);
}
private static class NewInstanceContentHandlerWithResultFactory<T>
implements ContentHandlerWithResult.Factory<T> {
private final Constructor<ContentHandlerWithResult<T>> ctor;
private NewInstanceContentHandlerWithResultFactory(Class<ContentHandlerWithResult<T>> clazz) {
try {
this.ctor = clazz.getDeclaredConstructor();
// allow private or package protected ctors
ctor.setAccessible(true);
} catch (NoSuchMethodException e) {
throw new IllegalArgumentException("ensure " + clazz + " has a no-args constructor", e);
}
}
@Override
public ContentHandlerWithResult<T> create() {
try {
return ctor.newInstance();
} catch (Exception e) {
throw new IllegalArgumentException("exception attempting to instantiate " + ctor, e);
}
}
}
}
}