es ik 分词插件 词库热加载源码分析

package org.wltea.analyzer.dic;

import java.io.IOException;

import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpHead;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

public class Monitor implements Runnable {

	private static CloseableHttpClient httpclient = HttpClients.createDefault();
	/*
	 * 上次更改时间
	 */
	private String last_modified;
	/*
	 * 资源属性
	 */
	private String eTags;
	
	/*
	 * 请求地址
	 */
	private String location; 
	
	public Monitor(String location) {
		this.location = location;
		this.last_modified = null;
		this.eTags = null;
	}
	/**
	 * 监控流程：
	 *  ①向词库服务器发送Head请求
	 *  ②从响应中获取Last-Modify、ETags字段值，判断是否变化
	 *  ③如果未变化，休眠1min，返回第①步
	 * 	④如果有变化，重新加载词典
	 *  ⑤休眠1min，返回第①步
	 */
	
	public void run() {

		//超时设置
		RequestConfig rc = RequestConfig.custom().setConnectionRequestTimeout(10*1000)
				.setConnectTimeout(10*1000).setSocketTimeout(15*1000).build();
		
		HttpHead head = new HttpHead(location);
		head.setConfig(rc);
		
		//设置请求头
		if (last_modified != null) {
			head.setHeader("If-Modified-Since", last_modified);
		}
		if (eTags != null) {
			head.setHeader("If-None-Match", eTags);
		}
		
		CloseableHttpResponse response = null;
		try {
			
			response = httpclient.execute(head);
			
			//返回200 才做操作
			if(response.getStatusLine().getStatusCode()==200){
			
				if (!response.getLastHeader("Last-Modified").getValue().equalsIgnoreCase(last_modified)
					||!response.getLastHeader("ETag").getValue().equalsIgnoreCase(eTags)) {

					// 远程词库有更新,需要重新加载词典，并修改last_modified,eTags
					Dictionary.getSingleton().reLoadMainDict();
					last_modified = response.getLastHeader("Last-Modified")==null?null:response.getLastHeader("Last-Modified").getValue();
					eTags = response.getLastHeader("ETag")==null?null:response.getLastHeader("ETag").getValue();
				}
			}else if (response.getStatusLine().getStatusCode()==304) {
				//没有修改，不做操作
				//noop
			}else{
				Dictionary.logger.info("remote_ext_dict {} return bad code {}" , location , response.getStatusLine().getStatusCode() );
			}

		} catch (Exception e) {
			Dictionary.logger.error("remote_ext_dict {} error!",e , location);
		}finally{
			try {
				if (response != null) {
					response.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	
}