org.codeseed.common.config.ConfigurationHandler.java Source code

Introduction

Here is the source code for org.codeseed.common.config.ConfigurationHandler.java

Source

/*
 * Copyright 2013 Jeremy Gustie
 *
 * 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 org.codeseed.common.config;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.util.Map;
import java.util.Objects;
import javax.annotation.Nullable;
import com.google.common.base.Converter;
import com.google.common.base.MoreObjects;
import com.google.common.collect.ImmutableMap;
import com.google.common.reflect.AbstractInvocationHandler;

/**
 * Handles the invocation of configuration methods.
 *
 * @author Jeremy Gustie
 */
class ConfigurationHandler extends AbstractInvocationHandler {

    /**
     * The source of property information.
     */
    private final PropertySource source;

    /**
     * Mapping of return types to the converter that should handle it.
     */
    private final Map<Type, Converter<String, ?>> converters;

    ConfigurationHandler(PropertySource source, Map<Type, Converter<String, ?>> converters) {
        this.source = checkNotNull(source);
        this.converters = ImmutableMap.copyOf(converters);
    }

    @Override
    protected Object handleInvocation(Object proxy, Method method, Object[] args) throws Throwable {
        final Class<?> declaringClass = method.getDeclaringClass();
        checkState(Configuration.class.isAssignableFrom(declaringClass), "expecting Configuration interface");
        checkState(declaringClass.isInterface(), "expecting interface");
        checkState(args.length == 0, "expecting zero argument method");
        return convert(method.getGenericReturnType(), getProperty(method));
    }

    protected String getProperty(Method method) {
        final String value = source.getProperty(method);
        if (value != null) {
            return value;
        } else {
            throw new MissingPropertyException(method);
        }
    }

    protected Object convert(Type type, String value) {
        final Converter<String, ?> converter = converters.get(type);
        if (converter != null) {
            return converter.convert(value);
        } else {
            throw new PropertyConversionException(type);
        }
    }

    @Override
    public boolean equals(@Nullable Object obj) {
        if (obj instanceof ConfigurationHandler) {
            ConfigurationHandler other = (ConfigurationHandler) obj;
            return Objects.equals(source, other.source) && Objects.equals(converters, other.converters);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return Objects.hash(source, converters);
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(getClass()).add("source", source).add("converters", converters)
                .toString();
    }

}