1.共享數(shù)據(jù)

package com.zzqsmile.servlet;

import javax.servlet.ServletContext;
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 HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        // this.getInitParameter()  //初始化參數(shù)
        // this.getServletConfig()  //獲取servlet配置
        // this.getServletContext() //servlet上下文

        ServletContext servletContext = this.getServletContext();

        String username = "zzqsmile";

        servletContext.setAttribute("username",username);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

package com.zzqsmile.servlet;

import javax.servlet.ServletContext;
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 GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();

        Object username = (String) servletContext.getAttribute("username");

        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html");
        resp.getWriter().println("名字："+username);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

2.獲取初始化參數(shù)

web.xml

<!--配置一些web應(yīng)用的初始化參數(shù)-->
    <context-param>
        <param-name>mysql_url</param-name>
        <param-value>jdbc:mysql://localhost:3306/mynatis</param-value>
    </context-param>

package com.zzqsmile.servlet;

import javax.servlet.ServletContext;
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 ServletDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        String mysql_url = servletContext.getInitParameter("mysql_url");
        resp.getWriter().println(mysql_url);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

3.請求轉(zhuǎn)發(fā)(200)

package com.zzqsmile.servlet;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
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 ServletDemo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        System.out.println("進(jìn)入了 ServletDemo4");
//        RequestDispatcher requestDispatcher = servletContext.getRequestDispatcher("/getp"); //轉(zhuǎn)發(fā)請求路徑
//        requestDispatcher.forward(req,resp);    //調(diào)用forward實(shí)現(xiàn)請求轉(zhuǎn)發(fā)
        servletContext.getRequestDispatcher("/getp").forward(req,resp);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

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4.讀取資源文件

Properties

• 在java目錄下新建properties (java_db.properties)
• 在resources目錄下新建properties (db.properties)

思路：需要一個(gè)文件流；

package com.zzqsmile.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class ServletDemo05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        InputStream resourceAsStream = this.getServletContext().getResourceAsStream("/WEB-INF/classes/com/zzqsmile/servlet/java_db.properties");
        InputStream resourceAsStream1 = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");

        Properties properties = new Properties();
        properties.load(resourceAsStream);
        properties.load(resourceAsStream1);


        String username = properties.getProperty("username");
        String password = properties.getProperty("password");

        String user = properties.getProperty("user");
        String pwd = properties.getProperty("pwd");

        resp.getWriter().println(username+":"+password);
        resp.getWriter().println(user+":"+pwd);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

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