com.dangdang.config.service.easyzk.support.localoverride.LocalOverrideFileLoader.java Source code

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Here is the source code for com.dangdang.config.service.easyzk.support.localoverride.LocalOverrideFileLoader.java

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/**
 * Copyright 1999-2014 dangdang.com.
 *  
 * 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 com.dangdang.config.service.easyzk.support.localoverride;

import java.io.IOException;
import java.io.InputStream;
import java.util.Map;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.base.Throwables;
import com.google.common.collect.Maps;

/**
 * 
 * 
 * @author <a href="mailto:wangyuxuan@dangdang.com">Yuxuan Wang</a>
 *
 */
public class LocalOverrideFileLoader {

    public static Map<String, String> loadLocalProperties(String rootNode, String group) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(rootNode) && !Strings.isNullOrEmpty(group),
                "rootNode or group cannot be empty.");

        Map<String, String> properties = null;
        final String localOverrideFile = findLocalOverrideFile();
        InputStream in = null;
        try {
            in = LocalOverrideFileLoader.class.getClassLoader().getResourceAsStream(localOverrideFile);
            if (in != null) {
                final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
                final DocumentBuilder builder = factory.newDocumentBuilder();

                final Document doc = builder.parse(in);
                final Element factoriesNode = Preconditions.checkNotNull(doc.getDocumentElement(),
                        "Root xml node node-factories not exists.");

                Node factoryNode = findChild(factoriesNode, "node-factory", "root", rootNode);
                if (factoriesNode != null) {
                    Node nodeGroup = findChild(factoryNode, "group", "id", group);
                    if (nodeGroup != null) {
                        NodeList childNodes = nodeGroup.getChildNodes();
                        int nodeCount = childNodes.getLength();
                        if (nodeCount > 0) {
                            properties = Maps.newHashMap();
                            for (int i = 0; i < nodeCount; i++) {
                                Node item = childNodes.item(i);
                                if (item.hasAttributes()) {
                                    NamedNodeMap attributes = item.getAttributes();
                                    Node keyAttr = attributes.getNamedItem("key");
                                    if (keyAttr != null) {
                                        String propKey = keyAttr.getNodeValue();
                                        String propVal = item.getFirstChild().getNodeValue();
                                        if (propKey != null && propVal != null) {
                                            properties.put(propKey, propVal);
                                        }
                                    }

                                }

                            }
                        }
                    }
                }
            }
        } catch (ParserConfigurationException e) {
            throw Throwables.propagate(e);
        } catch (SAXException e) {
            throw Throwables.propagate(e);
        } catch (IOException e) {
            throw Throwables.propagate(e);
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    // IGNORE
                }
            }
        }
        return properties;
    }

    /**
     * Find local override file name
     * 
     * @return
     */
    private static String findLocalOverrideFile() {
        String evnKey = System.getenv(DefaultConfigs.LOCAL_OVERRIDE_FILE_EVN_KEY);
        if (evnKey == null) {
            evnKey = DefaultConfigs.DEFAULT_LOCAL_OVERRIDE_FILE;
        }
        return evnKey;
    }

    /**
     * ?
     * 
     * @param parent
     *            
     * @param childNodeName
     *            ???
     * @param attrName
     *            ???
     * @param attrValue
     *            ?
     * @return
     */
    private static Node findChild(Node parent, String childNodeName, String attrName, String attrValue) {
        if (parent.hasChildNodes()) {
            final NodeList childNodes = parent.getChildNodes();
            final int nodeCount = childNodes.getLength();
            for (int i = 0; i < nodeCount; i++) {
                Node item = childNodes.item(i);
                if (item.hasAttributes()) {
                    Node attr = item.getAttributes().getNamedItem(attrName);
                    if (attr != null && attrValue.equals(attr.getNodeValue())) {
                        return item;
                    }
                }
            }
        }
        return null;
    }

}