1.引入

在Servlet3.0以后的版本提供了Servlet注解配置，大大簡化了代碼編寫。它可以替代xml文件的配置

2.代碼實現(xiàn)

<1>注解開發(fā)代碼如下：

@WebServlet(value = "/servlet1", initParams = {@WebInitParam(name = "charset", value = "utf-8")}) //【注：如果是只需要映射路徑則可以直接在雙引號中寫】 //@WebServlet("/servlet1") public class ServletDemo extends HttpServlet { }

<2>它等同于xml配置文件

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><servlet><servlet-name>ServletDemo </servlet-name><servlet-class>com.itheima.servlet.ServletDemo</servlet-class><init-param><param-name>charset</param-name><param-value>utf-8</param-value></init-param></servlet><servlet-mapping><servlet-name>ServletDemo </servlet-name><url-pattern>/servlet1</url-pattern></servlet-mapping> </web-app>

<3>ServletDemo獲取配置信息代碼

@WebServlet(value = "/servlet1", initParams = {@WebInitParam(name = "charset", value = "utf-8")}) //@WebServlet("/servlet1") public class ServletDemo extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletConfig servletConfig = this.getServletConfig();Enumeration<String> parameterNames = servletConfig.getInitParameterNames();while (parameterNames.hasMoreElements()) {String name = parameterNames.nextElement();String value = servletConfig.getInitParameter(name);System.out.println(name + "..." + value);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }打印結果： ------------------------------------------------------ charset...utf-8

3.自動注解開發(fā)的注解詳解

@Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface WebServlet { "指定Servlet的名稱" "--等效于web.xml文件<servlet>標簽下的<servlet-name>"String name() default ""; "--用于映射servlet" "等效于<url-pattern>" //兩個屬性只能寫一個String[] value() default {};String[] urlPatterns() default {}; "/指定servlet的加載時機" "等效于<load-on-startup>" //-1表示訪問時創(chuàng)建int loadOnStartup() default -1; "指定servlet的初始化參數(shù)" "等效于<init-param>"WebInitParam[] initParams() default {}; "指定servlet是否支持異步"boolean asyncSupported() default false; "指定servlet的小圖標"String smallIcon() default ""; "指定servlet的大圖標"String largeIcon() default ""; "指定servlet的描述信息"String description() default ""; "指定servlet的顯示名稱"String displayName() default ""; }

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