介绍

之前在邮政实习时，leader让我阅读tomcat的源代码，尝试自己实现远程部署项目的功能，于是便有了这此实践。
在Tomact中有一个Manager应用程序，它是用来管理已经部署的web应用程序，在这个应用程序中，ManagerServlet是他的主servlet，通过它我们可以获取tomcat的部分指标，远程管理web应用程序，不过这个功能会受到web应用程序部署中安全约束的保护。

当你请求ManagerServlet时，它会检查getPathInfo()返回的值以及相关的查询参数，以确定被请求的操作。它支持以下操作和参数(从servlet路径开始): 

我们可以通过ManagerServlet中getPathInfo()提供的操作，将自己的项目远程部署到服务器上，下面将贴出我的实践代码，在实践它之前你只需要引入httpclient包和commons包。

封装统一的远程请求管理类

封装此类用于方便client请求ManagerServlet：

import java.io.File;
import java.net.URL;
import java.net.URLEncoder;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.http.Header;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.Credentials;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.AuthCache;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.client.protocol.ClientContext;
import org.apache.http.impl.auth.BasicScheme;
import org.apache.http.impl.client.BasicAuthCache;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.PoolingClientConnectionManager;
import org.apache.http.protocol.BasicHttpContext;

public class TomcatManager {
  private static final String MANAGER_CHARSET = "UTF-8";
  private String username;
  private URL url;
  private String password;
  private String charset;
  private boolean verbose;
  private DefaultHttpClient httpClient;
  private BasicHttpContext localContext;

  /** constructor */
  public TomcatManager(URL url, String username) {
    this(url, username, "");
  }
  public TomcatManager(URL url, String username, String password) {
    this(url, username, password, "ISO-8859-1");
  }
  public TomcatManager(URL url, String username, String password, String charset) {
    this(url, username, password, charset, true);
  }
  public TomcatManager(URL url, String username, String password, String charset, boolean verbose) {
    this.url = url;
    this.username = username;
    this.password = password;
    this.charset = charset;
    this.verbose = verbose;
    
    // 创建网络请求相关的配置
    PoolingClientConnectionManager poolingClientConnectionManager = new PoolingClientConnectionManager();
    poolingClientConnectionManager.setMaxTotal(5);
    this.httpClient = new DefaultHttpClient(poolingClientConnectionManager);

    if (StringUtils.isNotEmpty(username)) {
      Credentials creds = new UsernamePasswordCredentials(username, password);

      String host = url.getHost();
      int port = url.getPort() > -1 ? url.getPort() : AuthScope.ANY_PORT;
      httpClient.getCredentialsProvider().setCredentials(new AuthScope(host, port), creds);

      AuthCache authCache = new BasicAuthCache();
      BasicScheme basicAuth = new BasicScheme();
      HttpHost targetHost = new HttpHost(url.getHost(), url.getPort(), url.getProtocol());
      authCache.put(targetHost, basicAuth);

      localContext = new BasicHttpContext();
      localContext.setAttribute(ClientContext.AUTH_CACHE, authCache);
    }
  }

  /** 根据指定的path部署并启动一个新的应用程序 */
  public TomcatManagerResponse deploy(String path, File war, boolean update) throws Exception {
    StringBuilder buffer = new StringBuilder("/deploy");
    buffer.append("?path=").append(URLEncoder.encode(path, charset));
    if (war != null) {
      buffer.append("&war=").append(URLEncoder.encode(war.toString(), charset));
    }
    if (update) {
      buffer.append("&update=true");
    }
    return invoke(buffer.toString());
  }

  /** 获取所有已部署的web应用程序的上下文路径。格式为path:status:sessions(活动会话数) */
  public TomcatManagerResponse list() throws Exception {
    StringBuilder buffer = new StringBuilder("/list");
    return invoke(buffer.toString());
  }

  /** 获取系统信息和JVM信息 */
  public TomcatManagerResponse serverinfo() throws Exception {
    StringBuilder buffer = new StringBuilder("/serverinfo");
    return invoke(buffer.toString());
  }

  /** 真正发送请求的方法 */
  private TomcatManagerResponse invoke(String path) throws Exception {
    HttpRequestBase httpRequestBase = new HttpGet(url + path);
    HttpResponse response = httpClient.execute(httpRequestBase, localContext);

    int statusCode = response.getStatusLine().getStatusCode();
    switch (statusCode) {
      case HttpStatus.SC_OK: // 200
      case HttpStatus.SC_CREATED: // 201
      case HttpStatus.SC_ACCEPTED: // 202
        break;
      case HttpStatus.SC_MOVED_PERMANENTLY: // 301
      case HttpStatus.SC_MOVED_TEMPORARILY: // 302
      case HttpStatus.SC_SEE_OTHER: // 303
      String redirectUrl = getRedirectUrl(response);
      this.url = new URL(redirectUrl);
      return invoke(path);
    }

    return new TomcatManagerResponse().setStatusCode(response.getStatusLine().getStatusCode())
        .setReasonPhrase(response.getStatusLine().getReasonPhrase())
        .setHttpResponseBody(IOUtils.toString(response.getEntity().getContent()));
  }
  
  /** 提取重定向URL */
  protected String getRedirectUrl(HttpResponse response) {
    Header locationHeader = response.getFirstHeader("Location");
    String locationField = locationHeader.getValue();
    // is it a relative Location or a full ?
    return locationField.startsWith("http") ? locationField : url.toString() + '/' + locationField;
  }
}