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185 lines (165 loc) · 5.73 KB
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/**
* Copyright 2012-2020 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.jackson;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.Module;
import com.fasterxml.jackson.databind.*;
import feign.Response;
import feign.codec.DecodeException;
import feign.codec.Decoder;
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.Reader;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
import static feign.Util.UTF_8;
import static feign.Util.ensureClosed;
/**
* Jackson decoder which return a closeable iterator. Returned iterator auto-close the
* {@code Response} when it reached json array end or failed to parse stream. If this iterator is
* not fetched till the end, it has to be casted to {@code Closeable} and explicity
* {@code Closeable#close} by the consumer.
* <p>
* <p>
* <p>
* Example: <br>
*
* <pre>
* <code>
* Feign.builder()
* .decoder(JacksonIteratorDecoder.create())
* .doNotCloseAfterDecode() // Required to fetch the iterator after the response is processed, need to be close
* .target(GitHub.class, "https://api.github.com");
* interface GitHub {
* {@literal @}RequestLine("GET /repos/{owner}/{repo}/contributors")
* Iterator<Contributor> contributors(@Param("owner") String owner, @Param("repo") String repo);
* }</code>
* </pre>
*/
public final class JacksonIteratorDecoder implements Decoder {
private final ObjectMapper mapper;
JacksonIteratorDecoder(ObjectMapper mapper) {
this.mapper = mapper;
}
@Override
public Object decode(Response response, Type type) throws IOException {
if (response.body() == null)
return null;
Reader reader = response.body().asReader(UTF_8);
if (!reader.markSupported()) {
reader = new BufferedReader(reader, 1);
}
try {
// Read the first byte to see if we have any data
reader.mark(1);
if (reader.read() == -1) {
return null; // Eagerly returning null avoids "No content to map due to end-of-input"
}
reader.reset();
return new JacksonIterator<Object>(actualIteratorTypeArgument(type), mapper, response,
reader);
} catch (RuntimeJsonMappingException e) {
if (e.getCause() != null && e.getCause() instanceof IOException) {
throw IOException.class.cast(e.getCause());
}
throw e;
}
}
private static Type actualIteratorTypeArgument(Type type) {
if (!(type instanceof ParameterizedType)) {
throw new IllegalArgumentException("Not supported type " + type.toString());
}
ParameterizedType parameterizedType = (ParameterizedType) type;
if (!Iterator.class.equals(parameterizedType.getRawType())) {
throw new IllegalArgumentException(
"Not an iterator type " + parameterizedType.getRawType().toString());
}
return ((ParameterizedType) type).getActualTypeArguments()[0];
}
public static JacksonIteratorDecoder create() {
return create(Collections.<Module>emptyList());
}
public static JacksonIteratorDecoder create(Iterable<Module> modules) {
return new JacksonIteratorDecoder(new ObjectMapper()
.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
.registerModules(modules));
}
public static JacksonIteratorDecoder create(ObjectMapper objectMapper) {
return new JacksonIteratorDecoder(objectMapper);
}
static final class JacksonIterator<T> implements Iterator<T>, Closeable {
private final Response response;
private final JsonParser parser;
private final ObjectReader objectReader;
private T current;
JacksonIterator(Type type, ObjectMapper mapper, Response response, Reader reader)
throws IOException {
this.response = response;
this.parser = mapper.getFactory().createParser(reader);
this.objectReader = mapper.reader().forType(mapper.constructType(type));
}
@Override
public boolean hasNext() {
if (current == null) {
current = readNext();
}
return current != null;
}
private T readNext() {
try {
JsonToken jsonToken = parser.nextToken();
if (jsonToken == null) {
return null;
}
if (jsonToken == JsonToken.START_ARRAY) {
jsonToken = parser.nextToken();
}
if (jsonToken == JsonToken.END_ARRAY) {
ensureClosed(this);
return null;
}
return objectReader.readValue(parser);
} catch (IOException e) {
// Input Stream closed automatically by parser
throw new DecodeException(response.status(), e.getMessage(), response.request(), e);
}
}
@Override
public T next() {
if (current != null) {
T tmp = current;
current = null;
return tmp;
}
T next = readNext();
if (next == null) {
throw new NoSuchElementException();
}
return next;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void close() throws IOException {
ensureClosed(this.response);
}
}
}