org.elasticsearch.script.mustache.MustacheScriptEngineService Maven / Gradle / Ivy
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Elasticsearch subproject :server
/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.script.mustache;
import com.github.mustachejava.Mustache;
import com.github.mustachejava.MustacheFactory;
import org.elasticsearch.common.Nullable;
import org.elasticsearch.common.component.AbstractComponent;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.io.FastStringReader;
import org.elasticsearch.common.io.UTF8StreamWriter;
import org.elasticsearch.common.io.stream.BytesStreamOutput;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.script.CompiledScript;
import org.elasticsearch.script.ExecutableScript;
import org.elasticsearch.script.ScriptEngineService;
import org.elasticsearch.script.ScriptException;
import org.elasticsearch.script.SearchScript;
import org.elasticsearch.search.lookup.SearchLookup;
import java.io.Reader;
import java.lang.ref.SoftReference;
import java.util.Collections;
import java.util.Map;
/**
* Main entry point handling template registration, compilation and
* execution.
*
* Template handling is based on Mustache. Template handling is a two step
* process: First compile the string representing the template, the resulting
* {@link Mustache} object can then be re-used for subsequent executions.
*/
public final class MustacheScriptEngineService extends AbstractComponent implements ScriptEngineService {
public static final String NAME = "mustache";
static final String CONTENT_TYPE_PARAM = "content_type";
static final String JSON_CONTENT_TYPE = "application/json";
static final String PLAIN_TEXT_CONTENT_TYPE = "text/plain";
/** Thread local UTF8StreamWriter to store template execution results in, thread local to save object creation.*/
private static ThreadLocal> utf8StreamWriter = new ThreadLocal<>();
/** If exists, reset and return, otherwise create, reset and return a writer.*/
private static UTF8StreamWriter utf8StreamWriter() {
SoftReference ref = utf8StreamWriter.get();
UTF8StreamWriter writer = (ref == null) ? null : ref.get();
if (writer == null) {
writer = new UTF8StreamWriter(1024 * 4);
utf8StreamWriter.set(new SoftReference<>(writer));
}
writer.reset();
return writer;
}
/**
* @param settings automatically wired by Guice.
* */
@Inject
public MustacheScriptEngineService(Settings settings) {
super(settings);
}
/**
* Compile a template string to (in this case) a Mustache object than can
* later be re-used for execution to fill in missing parameter values.
*
* @param template
* a string representing the template to compile.
* @return a compiled template object for later execution.
* */
@Override
public Object compile(String template, Map params) {
final MustacheFactory factory = new CustomMustacheFactory(isJsonEscapingEnabled(params));
Reader reader = new FastStringReader(template);
return factory.compile(reader, "query-template");
}
private boolean isJsonEscapingEnabled(Map params) {
String contentType = params.get(CONTENT_TYPE_PARAM);
return contentType == null || JSON_CONTENT_TYPE.equals(contentType);
}
@Override
public String[] types() {
return new String[] {NAME};
}
@Override
public String[] extensions() {
return new String[] {NAME};
}
@Override
public boolean sandboxed() {
return true;
}
@Override
public ExecutableScript executable(CompiledScript compiledScript,
@Nullable Map vars) {
return new MustacheExecutableScript(compiledScript, vars);
}
@Override
public SearchScript search(CompiledScript compiledScript, SearchLookup lookup,
@Nullable Map vars) {
throw new UnsupportedOperationException();
}
@Override
public void close() {
// Nothing to do here
}
/**
* Used at query execution time by script service in order to execute a query template.
* */
private class MustacheExecutableScript implements ExecutableScript {
/** Compiled template object wrapper. */
private CompiledScript template;
/** Parameters to fill above object with. */
private Map vars;
/**
* @param template the compiled template object wrapper
* @param vars the parameters to fill above object with
**/
public MustacheExecutableScript(CompiledScript template, Map vars) {
this.template = template;
this.vars = vars == null ? Collections.emptyMap() : vars;
}
@Override
public void setNextVar(String name, Object value) {
this.vars.put(name, value);
}
@Override
public Object run() {
BytesStreamOutput result = new BytesStreamOutput();
try (UTF8StreamWriter writer = utf8StreamWriter().setOutput(result)) {
((Mustache) template.compiled()).execute(writer, vars);
} catch (Exception e) {
logger.error("Error running " + template, e);
throw new ScriptException("Error running " + template, e);
}
return result.bytes();
}
@Override
public Object unwrap(Object value) {
return value;
}
}
}