标签：06 String request ServletContext import servlet javax
ServletContext对象：
1.概念：代表整个web应用，可以和程序的容器(服务器)来通信。
2.获取：
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo1")
public class ServletContextDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext对象获取：
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
*/
//1. 通过request对象获取
ServletContext context1 = request.getServletContext();
//2. 通过HttpServlet获取
ServletContext context2 = this.getServletContext();
System.out.println(context1);
System.out.println(context2);
System.out.println(context1 == context2);//true
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
3. 功能：
1. 获取MIME类型：
* MIME类型:在互联网通信过程中定义的一种文件数据类型
* 格式： 大类型/小类型 text/html image/jpeg
* 获取：String getMimeType(String file)
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo2")
public class ServletContextDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
* MIME类型:在互联网通信过程中定义的一种文件数据类型
* 格式： 大类型/小类型 text/html image/jpeg
* 获取：String getMimeType(String file)
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
//2. 通过HttpServlet获取
ServletContext context = this.getServletContext();
//3. 定义文件名称
String filename = "a.jpg";//image/jpeg
//4.获取MIME类型
String mimeType = context.getMimeType(filename);
System.out.println(mimeType);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
2. 域对象：共享数据
1. setAttribute(String name,Object value)
2. getAttribute(String name)
3. removeAttribute(String name)
* ServletContext对象范围：所有用户所有请求的数据
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo3")
public class ServletContextDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
//2. 通过HttpServlet获取
ServletContext context = this.getServletContext();
//设置数据
context.setAttribute("msg","haha");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo4")
public class ServletContextDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
//2. 通过HttpServlet获取
ServletContext context = this.getServletContext();
//获取数据
Object msg = context.getAttribute("msg");
System.out.println(msg);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
3. 获取文件的真实(服务器)路径
1. 方法：String getRealPath(String path)
String b = context.getRealPath("/b.txt");//web目录下资源访问
System.out.println(b);
String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问
System.out.println(c);
String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问
System.out.println(a);
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
@WebServlet("/servletContextDemo5")
public class ServletContextDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
// 通过HttpServlet获取
ServletContext context = this.getServletContext();
// 获取文件的服务器路径
String b = context.getRealPath("/b.txt");//web目录下资源访问
System.out.println(b);
// File file = new File(realPath);
String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问
System.out.println(c);
String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问
System.out.println(a);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
标签：06,String,request,ServletContext,import,servlet,javax 来源： https://www.cnblogs.com/newway644617704/p/14770874.html
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