一.Servlet相关注解
```text1.注解名称@WebServlet2.该注解使用前提Tomcat服务器需要支持servlet 3.0以上的规范才能使用该注解3.@WebServlet使用简化Servlet在web.xml中的配置<servlet><servlet-name>ServletDemo01</servlet-name><servlet-class>servlet01.ServletDemo01</servlet-class></servlet><servlet-mapping><servlet-name>ServletDemo01</servlet-name><url-pattern>/demo01</url-pattern></servlet-mapping>4.@WebServlet属性name:指的是Servlet的名称,对应web.xml中<servlet-name>urlPatterns:指定Servlet映射,对应web.xml中 <url-pattern>可以指定多个映射value:value属性和urlPatterns属性含义相同,都是指定url映射,但是如果我们在注解中只指定一个属性值,可以省略value属性名```java
/*** @WebServlet中的属性* name:指的是Servlet的名称,对应web.xml中<servlet-name>* urlPatterns:指定Servlet映射,对应web.xml中 <url-pattern>* value:value属性和urlPatterns属性含义相同,都是指定url映射,但是如果我们在注解中只指定一个属性值,可以省略value属性名*/
//@WebServlet(name = "ServletDemo01",urlPatterns = {"/ServletDemo01","/demo01"}) 正常
//@WebServlet(urlPatterns = "/ServletDemo01") 简化
@WebServlet("/ServletDemo01") //利用value属性可以省略的特性，更为简化
public class ServletDemo01 extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.getWriter().write("<b>ServletDemo01</b>");}
}二.修改注解创建Servlet模板
通过修改模板来简化我们的操作，不需要每次新建Servlet文件时都对@WebServlet注解进行修改
三.在IDEA中模拟HTTP请求
可以避免IDEA开发工具和浏览器之间反复切换新建一个http格式的文件,在里面书写GET/POST请求### 模拟浏览器向指定的服务器地址发出 GET请求//@no-cookie-jarGET http://localhost:8080/day10_Response/ServletDemo01###四.ServletConfig对象
1>在web.xml中添加配置信息
1.ServletConfig对象可以用来封装一些关于Servlet配置信息2.两种方法a.在web.xml中配置初始化参数<servlet><servlet-name>ServletConfigDemo01</servlet-name><servlet-class>servletconfig01.ServletConfigDemo01</servlet-class><!--在这个Servlet中配置一些初始化参数--><init-param><param-name>charset</param-name><param-value>UTF-8</param-value></init-param></servlet><servlet-mapping><servlet-name>ServletConfigDemo01</servlet-name><url-pattern>/config01</url-pattern></servlet-mapping>b.通过注解方式配置Servlet初始化参数@WebServlet(value = "/config02",initParams = @WebInitParam(name="charset",value = "UTF-8"))3.获取初始化参数System.out.println(getServletConfig().getInitParameter("charset"));2>在@WebServlet注解中添加配置信息
/*
* initParams = @WebInitParam(name="charset",value = "UTF-8")
* 相当于:
* <init-param><param-name>charset</param-name><param-value>UTF-8</param-value></init-param>
*/
@WebServlet( value = "/ServletConfigDemo02" ,initParams = @WebInitParam(name="charest",value="GBK"))
public class ServletConfigDemo02 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//利用getServletConfig()方法获取ServletConfig对象，调用getInitParameter()方法来获取参数System.out.println(getServletConfig().getInitParameter("charest"));}
}五.ServletContext对象
1.ServletContext代表当前web应用,每个web应用都只有唯一一个ServletContext对象
2.使用ServletContext来获取资源在硬盘上真实路径
/**
* 利用ServletContext的方法获取资源在硬盘上的真实路径
* public String getRealPath(String path):传入一个虚拟路径,返回一个资源真实路径
* InputStream getResourceAsStream(String path):传入一个虚拟路径,返回资源真实路径的输 入流
*/
注意:书写虚拟路径,以/开头,/代表当前应用
3.作为域对象使用
可以在ServletContext中存放一些key=value键值对,这些键值对可以被当前应用下的所有Servlet 共享
/**
* ServletContext对象中的方法:
* void setAttribute(String name, Object object):向ServletContext对象存入key=value键值对
* public Object getAttribute(String name):根据name(key)取出对应的value
*/
1>利用getRealPath()方法获取绝对路径，读取db.properties文件
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获取db.properties在硬盘的绝对路径String realPath = getServletContext().getRealPath("/WEB-INF/classes/db.properties");//通过Properties类获取db.properties里面的键值对信息Properties properties = new Properties();//利用输入流读取到db.properties文件FileInputStream fileInputStream = new FileInputStream(realPath);//将db.properties里的键值对写入到properties对象中properties.load(fileInputStream);System.out.println(properties);}2>getResourceAsStream()方法读取db.properties文件
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {InputStream resourceAsStream = getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");Properties properties = new Properties();properties.load(resourceAsStream);System.out.println(properties);}3>利用setAttribute()方法向ServletContext对象存入key=value键值对
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {ServletContext servletContext = getServletContext();String[] users = {"Jack","John","GGbond"};servletContext.setAttribute("username",users);//每个web应用都只有唯一一个ServletContext对象,所以上下两个对象实际上是同一个对象String[] username =(String[]) getServletContext().getAttribute("username");Arrays.stream(username).forEach(System.out::println);}
