ServletConfig对象
-
是什么
ServletConfig是javax.servlet.包下的一个接口,ServletConfig它是Servlet的一个配置对象;
ServletConfig是由tomcat容器创建,通过init方法传入给Servlet;
-
ServletConfig对象如何获取?
在GenericServlet里面定义了:
java
public ServletConfig getServletConfig() {
return this.config;
}
- 常用方法
java
getInitParameter(String parameterName); //根据参数名称获取指定的参数值
getInitParameterNames(); //获取所有的参数名称
- 需求:
获取servlet里面定义的参数
xml
<servlet>
<servlet-name>servletConfig</servlet-name>
<servlet-class>com.by.servlet.ServletConfigServlet</servlet-class>
<!--Servlet的初始化参数-->
<init-param>
<param-name>username</param-name>
<param-value>root</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>root123</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>servletConfig</servlet-name>
<url-pattern>/servletConfig</url-pattern>
</servlet-mapping>
java
package com.by.servlet;
import javax.servlet.*;
import javax.servlet.http.HttpServlet;
public class ServletConfigServlet extends HttpServlet {
@Override
public void service(ServletRequest servletRequest,
ServletResponse servletResponse) throws ServletException {
//1.获取ServletConfig对象
ServletConfig servletConfig = getServletConfig();
//2.获取Servlet中的初始化参数
String username = servletConfig.getInitParameter("username");
System.out.println(username);
String password = servletConfig.getInitParameter("password");
System.out.println(password);
}
}
思考:param参数可不可以在另外的Servlet中获取? 不能
java
public class ServletConfigServlet2 extends HttpServlet {
@Override
public void goGet(ServletRequest servletRequest,
ServletResponse servletResponse) throws ServletException {
//1.获取ServletConfig对象
ServletConfig servletConfig = getServletConfig();
//2.获取Servlet中的初始化参数
String username = servletConfig.getInitParameter("username");//不能获取
System.out.println(username);
String password = servletConfig.getInitParameter("password");//不能获取
System.out.println(password);
}
}
ServletContext对象
-
是什么
ServletContext是javax.servlet包下的一个接口,又称上下文对象,是配置对象也是一个域对象;
当服务器启动时,会为服务器中的每一个web应用程序创建一个ServletContext对象;
在web应用中的servlet要想实现资源的共享,可以通过ServletContext来完成;
-
如何获取这个对象:
java
public ServletContext getServletContext() {
//获取ServletContext对象
return this.getServletConfig().getServletContext();
}
- 这个对象里面也有很多方法:
java
getInitParameter() //获取指定参数名称的全局参数值
getRealPath(String path) //获得当前项目的服务器磁盘路径
getContextPath() //获取项目的根路径
getAttribute(String parameterName) //获取ServletContext域中指定名称的参数值;
setAttribute(String paramterName,Object parameterValue) //存储参数到ServletContext域中;
removeAttribute(String parameterNam) //将ServletContext域中指定名称的参数移除;
- 需求
获取servlet里面定义的参数
xml
<context-param>
<param-name>username</param-name>
<param-value>root</param-value>
</context-param>
<context-param>
<param-name>password</param-name>
<param-value>root456</param-value>
</context-param>
java
package com.by.servlet;
import javax.servlet.*;
import javax.servlet.http.HttpServlet;
public class ServletContextServlet extends HttpServlet {
@Override
public void service(ServletRequest servletRequest,
ServletResponse servletResponse) throws ServletException {
//获取ServletContext对象
ServletContext servletContext = getServletContext();
//1.获取全局初始化参数
String username = servletContext.getInitParameter("username");
System.out.println(username);
String password = servletContext.getInitParameter("password");
System.out.println(password);
//2.获取服务器真实路径
String upload = servletContext.getRealPath("");
System.out.println(upload);
//3.获取项目的根路径
String contextPath = servletContext.getContextPath();
System.out.println(contextPath);
//4.往ServletContext域中,存储一个名称为msg的属性,值为"hello"
String str = "hello";
servletContext.setAttribute("msg",str);
}
}
思考:param参数可不可以在另外的Servlet中获取? 不能
java
package com.by.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
public class ServletContextServlet2 extends HttpServlet {
@Override
public void doGet(ServletRequest servletRequest,
ServletResponse servletResponse) throws ServletException {
//从ServletContext域中取出msg的值
ServletContext servletContext = getServletContext();
//1.获取全局初始化参数
String username = servletContext.getInitParameter("username");
System.out.println(username);
String password = servletContext.getInitParameter("password");
System.out.println(password);
//2.获得msg属性
Object msg = servletContext.getAttribute("msg");//能获取
System.out.println(msg);
}
}
java
package com.by.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
public class ServletContextServlet3 extends HttpServlet {
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException {
//1.获取ServletContext对象
ServletContext servletContext = getServletContext();
//将ServletContext域中的msg参数移除
servletContext.removeAttribute("msg");
}
}
xml
<servlet>
<servlet-name>context3=</servlet-name>
<servlet-class>com.by.servlet.ServletContextServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>context3=</servlet-name>
<url-pattern>/context=</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>context2</servlet-name>
<servlet-class>com.by.servlet.ServletContextServlet2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>context2</servlet-name>
<url-pattern>/context2</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>context3</servlet-name>
<servlet-class>com.by.servlet.ServletContextServlet3</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>context3</servlet-name>
<url-pattern>/context3</url-pattern>
</servlet-mapping>
Request对象
- 是什么
ServletRequest是一个接口,用户访问服务器,服务器会生成一个对象包含了http所有请求头,由于使用的是http协议,所以该对象的名字叫HttpServletRequest
- 常用的方法
java
getRequestURL() //获取的完整的URL,即统一资源定位符
getRequestURI() //获取资源的名字,即统一资源标识符
getQueryString() //获取一个url参数部分
getRemoteAddr() //返回的是客户端的ip地址
getRemoteUser() //返回的是客户端的用户
getRemotePort() //返回的是客户端的主机的端口号
getRemoteHost() //返回的是客户端的主机地址
getCookie() //获取Cookie对象
getSession() //获取Session对象
getLocalName() //获取Web服务器主机的名字
getServletContext() //获取上下文对象的
setCharacterEncoding() //设置编码集的
getParameter() //获取前端传过来的数据
setAttribute() //将数据设置给request对象
geAttribute() //获取request对象中的数据
- servlet实例
java
package com.by.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class RequestServlet extends HttpServlet {
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws Exception {
doGet(request, response);
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws Exception{
//获取一个完整的url
//http://localhost:8080/01_servlet_HelloWorld_war/request1
System.out.println(request.getRequestURL());
//获取资源的名字
//比如:http://localhost:8080/day42_xkh/request1
System.out.println(request.getRequestURI());///01_servlet_HelloWorld_war/request1
//获取一个url的参数部分
//比如 http://localhost:8080/01_servlet_HelloWorld_war/request1?username=goudan
System.out.println(request.getParameter("username"));
//获取前端传送过来的数据
request.setCharacterEncoding("utf-8");//设置请求的编码集
//给request这个对象设置数据
request.setAttribute("name","狗蛋");
//获取request对象的值
request.getAttribute("name");
//获取上下文对象
ServletContext servletContext = request.getServletContext();
//转发
request.getRequestDispatcher("target.jsp").forward(request,response);
}
}
xml
<servlet>
<servlet-name>request</servlet-name>
<servlet-class>com.by.servlet.RequestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>request</servlet-name>
<url-pattern>/context</url-pattern>
</servlet-mapping>
Response对象
- 是什么
响应对象,把数据返回给客户端
我们的Servlet紧紧围绕着两个点(Request,Response)请求和响应
- 常用方法
java
setHeader() //设置响应头的参数
setContentType() //设置字符编码集
getWriter() //获取字符输出流对象
addCookie() //对浏览器新增一个Cookie
sendRedirect() //重定向
- servlet实例
java
package com.by.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class ResponseServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws Exception{
/**************乱码问题*****/
//方式一
response.setHeader("Content-Type",
"text/html;charset=utf-8");//通知浏览器使用utf-8解码
//方式二
response.setContentType("text/html;charset=utf-8;aaa=bbb"); //包含方法一的两个功能
//向客户端发送响应数据
response.getWriter().write("<h1>hello<h1>");
/************重定向***********/
//方式一
//在响应头中添加302状态码,告诉浏览器需要进行重定向
response.setStatus(302);
//在响应头中添加Location,指定重定向的位置
response.setHeader("Location", "http://www.baidu.com");
//方式二
response.sendRedirect("http://www.baidu.com"); //包含方法一的两个功能
}
}
xml
<servlet>
<servlet-name>response</servlet-name>
<servlet-class>com.by.servlet.ResponseServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>response</servlet-name>
<url-pattern>/response</url-pattern>
</servlet-mapping>