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133 lines (114 loc) · 3.93 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 example.wikipedia;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import feign.Feign;
import feign.Logger;
import feign.Param;
import feign.RequestLine;
import feign.gson.GsonDecoder;
public class WikipediaExample {
static ResponseAdapter<Page> pagesAdapter = new ResponseAdapter<Page>() {
@Override
protected String query() {
return "pages";
}
@Override
protected Page build(JsonReader reader) throws IOException {
Page page = new Page();
while (reader.hasNext()) {
String key = reader.nextName();
if (key.equals("pageid")) {
page.id = reader.nextLong();
} else if (key.equals("title")) {
page.title = reader.nextString();
} else {
reader.skipValue();
}
}
return page;
}
};
public static void main(String... args) throws InterruptedException {
Gson gson = new GsonBuilder()
.registerTypeAdapter(new TypeToken<Response<Page>>() {}.getType(), pagesAdapter)
.create();
Wikipedia wikipedia = Feign.builder()
.decoder(new GsonDecoder(gson))
.logger(new Logger.ErrorLogger())
.logLevel(Logger.Level.BASIC)
.target(Wikipedia.class, "https://en.wikipedia.org");
System.out.println("Let's search for PTAL!");
Iterator<Page> pages = lazySearch(wikipedia, "PTAL");
while (pages.hasNext()) {
System.out.println(pages.next().title);
}
}
/**
* this will lazily continue searches, making new http calls as necessary.
*
* @param wikipedia used to search
* @param query see {@link Wikipedia#search(String)}.
*/
static Iterator<Page> lazySearch(final Wikipedia wikipedia, final String query) {
final Response<Page> first = wikipedia.search(query);
if (first.nextOffset == null) {
return first.iterator();
}
return new Iterator<Page>() {
Iterator<Page> current = first.iterator();
Long nextOffset = first.nextOffset;
@Override
public boolean hasNext() {
while (!current.hasNext() && nextOffset != null) {
System.out.println("Wow.. even more results than " + nextOffset);
Response<Page> nextPage = wikipedia.resumeSearch(query, nextOffset);
current = nextPage.iterator();
nextOffset = nextPage.nextOffset;
}
return current.hasNext();
}
@Override
public Page next() {
return current.next();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
public static interface Wikipedia {
@RequestLine("GET /w/api.php?action=query&continue=&generator=search&prop=info&format=json&gsrsearch={search}")
Response<Page> search(@Param("search") String search);
@RequestLine("GET /w/api.php?action=query&continue=&generator=search&prop=info&format=json&gsrsearch={search}&gsroffset={offset}")
Response<Page> resumeSearch(@Param("search") String search, @Param("offset") long offset);
}
static class Page {
long id;
String title;
}
public static class Response<X> extends ArrayList<X> {
/**
* when present, the position to resume the list.
*/
Long nextOffset;
}
}