org.jclouds.http.UriTemplates.java Source code

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Here is the source code for org.jclouds.http.UriTemplates.java

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/*
 * 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.jclouds.http;

import static com.google.common.base.Preconditions.checkNotNull;

import java.util.Map;

import com.google.common.collect.Lists;

/**
 * 
 * @author Adrian Cole
 * 
 */
public class UriTemplates {

    /**
     * 
     * @param template
     *           URI template that can be in level 1 <a href="http://tools.ietf.org/html/rfc6570">RFC6570</a> form.
     * 
     * @param variables
     *           to the URI template
     * @return expanded template, leaving any unresolved parameters literal
     */
    public static String expand(String template, Map<String, ?> variables) {
        if (checkNotNull(template, "template").length() < 3)
            return template.toString(); // skip expansion if there's no valid variables set. ex. {a} is the first valid
        checkNotNull(variables, "variables for %s", template);

        boolean inVar = false;
        StringBuilder var = new StringBuilder();
        StringBuilder builder = new StringBuilder();
        for (char c : Lists.charactersOf(template)) {
            switch (c) {
            case '{':
                inVar = true;
                break;
            case '}':
                inVar = false;
                String key = var.toString();
                Object value = variables.get(var.toString());
                if (value != null)
                    builder.append(value);
                else
                    builder.append('{').append(key).append('}');
                var = new StringBuilder();
                break;
            default:
                if (inVar)
                    var.append(c);
                else
                    builder.append(c);
            }
        }
        return builder.toString();
    }
}