org.apache.kyuubi.util.reflect.DynClasses Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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.apache.kyuubi.util.reflect;
import java.util.LinkedHashSet;
import java.util.Set;
/** Copied from iceberg-common */
public class DynClasses {
private DynClasses() {}
public static Builder builder() {
return new Builder();
}
public static class Builder {
private ClassLoader loader = Thread.currentThread().getContextClassLoader();
private Class foundClass = null;
private boolean nullOk = false;
private Set classNames = new LinkedHashSet<>();
private Builder() {}
/**
* Set the {@link ClassLoader} used to lookup classes by name.
*
* If not set, the current thread's ClassLoader is used.
*
* @param newLoader a ClassLoader
* @return this Builder for method chaining
*/
public Builder loader(ClassLoader newLoader) {
this.loader = newLoader;
return this;
}
/**
* Checks for an implementation of the class by name.
*
* @param className name of a class
* @return this Builder for method chaining
*/
public Builder impl(String className) {
classNames.add(className);
if (foundClass != null) {
return this;
}
try {
this.foundClass = Class.forName(className, true, loader);
} catch (ClassNotFoundException e) {
// not the right implementation
}
return this;
}
/**
* Instructs this builder to return null if no class is found, rather than throwing an
* Exception.
*
* @return this Builder for method chaining
*/
public Builder orNull() {
this.nullOk = true;
return this;
}
/**
* Returns the first implementation or throws ClassNotFoundException if one was not found.
*
* @param Java superclass
* @return a {@link Class} for the first implementation found
* @throws ClassNotFoundException if no implementation was found
*/
@SuppressWarnings("unchecked")
public Class buildChecked() throws ClassNotFoundException {
if (!nullOk && foundClass == null) {
throw new ClassNotFoundException(
"Cannot find class; alternatives: " + String.join(", ", classNames));
}
return (Class) foundClass;
}
/**
* Returns the first implementation or throws RuntimeException if one was not found.
*
* @param Java superclass
* @return a {@link Class} for the first implementation found
* @throws RuntimeException if no implementation was found
*/
@SuppressWarnings("unchecked")
public Class build() {
if (!nullOk && foundClass == null) {
throw new RuntimeException(
"Cannot find class; alternatives: " + String.join(", ", classNames));
}
return (Class) foundClass;
}
}
}