zipkin2.elasticsearch.internal.JsonReaders Maven / Gradle / Ivy
/*
* Copyright 2015-2019 The OpenZipkin 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 zipkin2.elasticsearch.internal;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import zipkin2.internal.Nullable;
/**
* Utilities used here aim to reduce allocation overhead for common requests. It does so by skipping
* unrelated fields. This is used for responses which could be large.
*/
public final class JsonReaders {
/**
* Navigates to a field of a JSON-serialized object. For example,
*
* {@code
* JsonParser status = enterPath(JsonAdapters.jsonParser(stream), "message", "status");
* if (status != null) throw new IllegalStateException(status.nextString());
* }
*/
@Nullable public static JsonParser enterPath(JsonParser parser, String path1, String path2)
throws IOException {
return enterPath(parser, path1) != null ? enterPath(parser, path2) : null;
}
@Nullable public static JsonParser enterPath(JsonParser parser, String path) throws IOException {
if (!checkStartObject(parser, false)) return null;
JsonToken value;
while ((value = parser.nextValue()) != JsonToken.END_OBJECT) {
if (value == null) {
// End of input so ignore.
return null;
}
if (parser.getCurrentName().equalsIgnoreCase(path) && value != JsonToken.VALUE_NULL) {
return parser;
} else {
parser.skipChildren();
}
}
return null;
}
public static List collectValuesNamed(JsonParser parser, String name) throws IOException {
checkStartObject(parser, true);
Set result = new LinkedHashSet<>();
visitObject(parser, name, result);
return new ArrayList<>(result);
}
static void visitObject(JsonParser parser, String name, Set result) throws IOException {
checkStartObject(parser, true);
JsonToken value;
while ((value = parser.nextValue()) != JsonToken.END_OBJECT) {
if (value == null) {
// End of input so ignore.
return;
}
if (parser.getCurrentName().equals(name)) {
result.add(parser.getText());
} else {
visitNextOrSkip(parser, name, result);
}
}
}
static void visitNextOrSkip(JsonParser parser, String name, Set result)
throws IOException {
switch (parser.currentToken()) {
case START_ARRAY:
JsonToken token;
while ((token = parser.nextToken()) != JsonToken.END_ARRAY) {
if (token == null) {
// End of input so ignore.
return;
}
visitObject(parser, name, result);
}
break;
case START_OBJECT:
visitObject(parser, name, result);
break;
default:
// Skip current value.
}
}
static boolean checkStartObject(JsonParser parser, boolean shouldThrow) throws IOException {
try {
JsonToken currentToken = parser.currentToken();
// The parser may not be at a token, yet. If that's the case advance.
if (currentToken == null) currentToken = parser.nextToken();
// If we are still not at the expected token, we could be an another or an empty body.
if (currentToken == JsonToken.START_OBJECT) return true;
if (shouldThrow) {
throw new IllegalArgumentException("Expected start object, was " + currentToken);
}
return false;
} catch (Throwable e) { // likely not json
if (shouldThrow) throw e;
return false;
}
}
JsonReaders() {
}
}