前面我们已经分析过了启动过程,现在server可以接受client端的request,并进行处理。
request由servlet进行处理,并返回结果。现在我们看一下,web.xml文件中的REST API是如何和servlet相对应的。
web.xml
下面是web.xml文件中关于connector的servlet的配置信息。
<!-- Connectors servlet -->
<servlet>
<servlet-name>v1.ConnectorsServlet</servlet-name>
<servlet-class>org.apache.sqoop.server.v1.ConnectorServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>v1.ConnectorsServlet</servlet-name>
<url-pattern>/v1/connectors/*</url-pattern>
</servlet-mapping>
从上面的配置信息我们可以看出关于URL中关于/v1/connectors/*的请求信息都被转发给v1.ConnectorsServlet来进行处理,也就是org.apache.sqoop.server.v1.ConnectorServlet类。
SqoopProtocolServlet类
org.apache.sqoop.server.v1包中实现的所有servlet都继承了SqoopProtocolServlet类。SqoopProtocolServlet类继承了HttpServlet类。总体的继承关系如下图所示:
servlet类间关系图.pngSqoopProtocolServlet继承了HttpServlet类,实现了doGet, doPut, doPost, doDelete四个方法。并实现了handleGetRequest,handlePostRequest,handlePutRequest, handleDeleteRequest四个方法用于子类进行继承。
默认的方法实现为各自调用do##的实现。
如下所示:
@Override
protected final void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
RequestContext rctx = new RequestContext(req, resp);
try {
JsonBean bean = handleGetRequest(rctx);
if (bean != null) {
sendSuccessResponse(rctx, bean);
}
} catch (Exception ex) {
LOG.error("Exception in GET " + rctx.getPath(), ex);
sendErrorResponse(rctx, ex);
}
}
====================
protected JsonBean handleGetRequest(RequestContext ctx) throws Exception {
super.doGet(ctx.getRequest(), ctx.getResponse());
return null;
}
ConnectorServlet类
ConnectorServlet类仅仅将其请求委托给connectorRequestHandler进行处理。主要实现如下:
@SuppressWarnings("serial")
public class ConnectorServlet extends SqoopProtocolServlet {
private RequestHandler connectorRequestHandler;
public ConnectorServlet() {
connectorRequestHandler = new ConnectorRequestHandler();
}
@Override
protected JsonBean handleGetRequest(RequestContext ctx) throws Exception {
return connectorRequestHandler.handleEvent(ctx);
}
}
ConnectorRequestHandler类
ConnectorRequestHandler类实现RequestHandler接口。主要的功能在于对client端发送的request请求进行处理。
其处理的主要步骤为:
- 判断是否为GET (connector只支持HTTP GET方法)
- 判断是根据id/name还是读取所有的信息
- 将请求进一步的委托给ConnectorManager读取信息
- 返回结果
源代码如下:
public class ConnectorRequestHandler implements RequestHandler {
private static final Logger LOG = Logger.getLogger(ConnectorRequestHandler.class);
private static final String CONNECTORS_PATH = "connectors";
public ConnectorRequestHandler() {
LOG.info("ConnectorRequestHandler initialized");
}
@Override
public JsonBean handleEvent(RequestContext ctx) {
// connector only support GET requests
if (ctx.getMethod() != Method.GET) {
throw new SqoopException(ServerError.SERVER_0002, "Unsupported HTTP method for connector:"
+ ctx.getMethod());
}
List<MConnector> connectors;
Map<Long, ResourceBundle> configParamBundles;
Locale locale = ctx.getAcceptLanguageHeader();
String cIdentifier = ctx.getLastURLElement();
LOG.info("ConnectorRequestHandler handles cid: " + cIdentifier);
if (ctx.getPath().contains(CONNECTORS_PATH) || cIdentifier.equals("all")) {
connectors = ConnectorManager.getInstance().getConnectorConfigurables();
configParamBundles = ConnectorManager.getInstance().getResourceBundles(locale);
AuditLoggerManager.getInstance().logAuditEvent(ctx.getUserName(),
ctx.getRequest().getRemoteAddr(), "get", "connectors", "all");
// Authorization check
connectors = AuthorizationEngine.filterResource(MResource.TYPE.CONNECTOR, connectors);
return new ConnectorsBean(connectors, configParamBundles);
} else {
// NOTE: we now support using unique name as well as the connector id
// NOTE: connectorId is a fallback for older sqoop clients if any, since we want to primarily use unique conenctorNames
long cId = HandlerUtils.getConnectorIdFromIdentifier(cIdentifier);
configParamBundles = new HashMap<Long, ResourceBundle>();
MConnector connector = ConnectorManager.getInstance().getConnectorConfigurable(cId);
configParamBundles.put(cId, ConnectorManager.getInstance().getResourceBundle(cId, locale));
AuditLoggerManager.getInstance().logAuditEvent(ctx.getUserName(),
ctx.getRequest().getRemoteAddr(), "get", "connector", String.valueOf(cIdentifier));
// Authorization check
AuthorizationEngine.readConnector(String.valueOf(connector.getPersistenceId()));
return new ConnectorBean(Arrays.asList(connector), configParamBundles);
}
}
}
网友评论