Java中的跨域請求

與 ABAP 中類似的邏輯。

使用名為“HelloWorldServlet”的 servlet 在 Java 中創建一個動態 Web 項目：

將以下實現源代碼復制到 Servlet 中：

public class HelloWorldServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public HelloWorldServlet() {
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {	
    	List<String> allowedUserId = Arrays.asList(getServletContext().getInitParameter("userIds").trim().split(","));
        String clientOrigin = request.getHeader("origin");
        String ipAddress = request.getHeader("x-forwarded-for");
        if (ipAddress == null) {
            ipAddress = request.getRemoteAddr();
        }
        String userId = request.getParameter("userId");
        if( userId != null)
        	userId = userId.trim();
        if( allowedUserId.contains(userId)){
        	response.setHeader("Access-Control-Allow-Origin", clientOrigin);
        }
        if( ipAddress.equals("0:0:0:0:0:0:0:1"))
        	response.getWriter().println("local one");
        else
        	response.getWriter().println("Hello World!");
    }
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}

WEB-INF 文件夾中的 web.xml，允許的用戶 ID 列在節點 <context-param> 中。

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	id="WebApp_ID" version="2.5">
	<display-name>JerryTest</display-name>
	<welcome-file-list>
		<welcome-file>Hello</welcome-file>
		<welcome-file>index.html</welcome-file>
	</welcome-file-list>
	<context-param>
		<param-name>userIds</param-name>
		<param-value>i042416,i042417,i042418</param-value>
	</context-param>
	<servlet>
		<description></description>
		<display-name>HelloWorldServlet</display-name>
		<servlet-name>HelloWorldServlet</servlet-name>
		<servlet-class>helloworld.HelloWorldServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<!-- http://stackoverflow.com/questions/4140448/difference-between-and-in-servlet-mapping-url-pattern -->
		<servlet-name>HelloWorldServlet</servlet-name>
		<url-pattern>/Hello</url-pattern>
	</servlet-mapping>
</web-app>

現在使用列表中未包含的用戶 id 訪問 servlet，請求失敗：

并通過請求中指定的允許用戶 ID 執行正面測試：

請求成功處理并返回瀏覽器：