16-day14 dark horse javaweb notes servlet & HTTP & request

Servlet:

Architecture of Servlet

servlet is an interface, and there are two implementation classes:

1.GenericServlet -- abstract class
2.HttpServlet  -- abstract class

GenericServlet:

Other methods in the Servlet interface are implemented by default, and only the service() method is used as an abstraction

When defining Servlet classes in the future, you can inherit GenericServlet and implement the service() method

HttpServlet:

An encapsulation of http protocol to simplify operation

		1. Define class inheritance HttpServlet
		2. make carbon copies doGet/doPost method

Servlet related configuration

urlpartten:Servlet access path

1. A Servlet can define multiple access paths:

   @WebServlet({"/d4","/dd4","/ddd4"})
   

2. Path definition rules

   1. 1. /xxx: Path matching
      2. /xxx/xxx:Multi layer path, directory structure
      3. *.do: Extension matching
      

HTTP:

Hyper Text Transfer Protocol

Transmission protocol:

Defines the format of sending data when the client and server communicate

characteristic:

		1. be based on TCP/IP Advanced protocol
		2. Default port number:80
		3. Request based/Response model:One request corresponds to one response
		4. Stateless: each request is independent of each other and cannot interact with data

Historical version:

		* 1.0: Each request response establishes a new connection
		* 1.1: Multiplex connection

Request message data format

1. Request line

		Request mode request url Request protocol/edition
		GET /login.html	HTTP/1.1
		
		
		Request method:
				* HTTP There are 7 request modes in the protocol, and 2 are commonly used
				* GET: 
					1. Request parameters are in the request line, in url After.
					2. Requested url Length limited
					3. Not very safe
				* POST: 
					1. The request parameter is in the request body
					2. Requested url Unlimited length
					3. Relative safety

1. Request header: the client browser tells the server some information

Request header name: Request header value


Common request headers:
1. User-Agent: The browser tells the server that I can access the version information of the browser you use
	The header information can be obtained on the server side to solve the compatibility problem of the browser
	
2.Referer: http://localhost/login.html
 Tell the server that I(Current request)Where do you come from?
effect:
						1. Anti theft chain:
						2. Statistical work:

1. Request blank line

An empty line is used to split the request header and request body of a POST request.

1. Request body (body):

encapsulation POST Of the request parameters of the request message


String format:
POST /login.html	HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Referer: http://localhost/login.html
Connection: keep-alive
Upgrade-Insecure-Requests: 1
		
username=zhangsan	

Request:

Principle of request object and response object

1. request and response The object is created by the server. Let's use them
2. request Object is to get the request message, response Object to set the response message

request object inheritance architecture:

	ServletRequest		--	Interface
		|	inherit
	HttpServletRequest	-- Interface
		|	realization
	org.apache.catalina.connector.RequestFacade class(tomcat)

request function:

1. Get request message data

Get request line data

GET /day14/demo1?name=zhangsan HTTP/1.1

method:
1. Get request method: GET
					* String getMethod()  
2. (*)Get virtual directory:/day14
					* String getContextPath()
3. obtain Servlet route: /demo1
					* String getServletPath()
4. obtain get Mode request parameters: name=zhangsan
					* String getQueryString()
5. (*)Get request URI: /day14/demo1
					* String getRequestURI():		/day14/demo1
					* StringBuffer getRequestURL()  :http://localhost/day14/demo1
					* URL:Uniform resource locator: http://localhost/day14/demo1 	 The People's Republic of China
					* URI: Uniform resource identifier : /day14/demo1					republic
				
6. Obtain agreement and version: HTTP/1.1
					* String getProtocol()

7. Gets the name of the client IP Address:
					* String getRemoteAddr()

1. Get request header data

method:

(*)String getHeader(String name):Get the value of the request header by the name of the request header
Enumeration<String> getHeaderNames():Get all request header names

3. Obtain the requestor data:

Request body: only the POST request method can have a request body. The request parameters of the POST request are encapsulated in the request body

Steps:

1. Get stream object

BufferedReader getReader(): Gets the character input stream. Only character data can be manipulated
ServletInputStream getInputStream(): Get byte input stream, which can operate on all types of data
		Explain after uploading knowledge points

1. Then get the data from the stream object

Other functions:

1. General methods for obtaining request parameters: the following methods can be used to obtain request parameters regardless of get or post request methods

1. String getParameter(String name):Get parameter value according to parameter name    username=zs&password=123
2. String[] getParameterValues(String name):Gets an array of parameter values based on parameter names  hobby=xx&hobby=game
3. Enumeration<String> getParameterNames():Gets the parameter names of all requests
4. Map<String,String[]> getParameterMap():Get all parameters map aggregate

Chinese garbled Code:

* get Method: tomcat 8 Already get The problem of garbled code has been solved
* post Method: garbled code
					* Solution: before getting parameters, set request Coding of request.setCharacterEncoding("utf-8");

1. Request forwarding: a resource jump mode within the server

1. adopt request Object get request forwarder object: RequestDispatcher getRequestDispatcher(String path)
2. use RequestDispatcher Object to forward: forward(ServletRequest request, ServletResponse response) 

characteristic:

1. The browser address bar path does not change
2. It can only be forwarded to the internal resources of the current server.
3. Forwarding is a request

1. Shared data:

* Domain object: an object with scope that can share data within the scope
* request Domain: represents the scope of a request. It is generally used to share data among multiple resources requesting forwarding

method:

1. void setAttribute(String name,Object obj):Store data
2. Object getAttitude(String name):Get value by key
3. void removeAttribute(String name):Remove key value pairs with key

1. Get ServletContext:

ServletContext getServletContext()

Case: user login

• User login case requirements:

	1.to write login.html Login page
		username & password Two input boxes
	2.use Druid Database connection pool technology,operation mysql，day14 In database user surface
	3.use JdbcTemplate Technology packaging JDBC
	4.Login succeeded, jump to SuccessServlet Show: login succeeded! user name,Welcome
	5.Login failed, jump to FailServlet Display: login failure, user name or password error

Development steps

1. Create project, import html page, configuration file, jar package

Note: lib needs to be placed under Web inf

Login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form method="post" action="#">
        username:<input type="text" name="username"><br>
        password:<input type="password" name="password"><br>
        <input type="submit" value="Submit">
    </form>
</body>
</html>

1. Create database environment

CREATE DATABASE day14;
USE day14;
CREATE TABLE USER(
		id INT PRIMARY KEY AUTO_INCREMENT,
			username VARCHAR(32) UNIQUE NOT NULL,
			PASSWORD VARCHAR(32) NOT NULL
);

#insert data
insert into user(username,password) VALUES ("admin","password");

1. Create class User

package User;

public class User {
    private int id;
    private String username;
    private String password;

    public User() {
    }

    public User(int id, String username, String password) {

        this.id = id;
        this.username = username;
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

1. Create the package cn.itcast.util and write the tool class JDBCUtils

package druid;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtils {
    private static DataSource ds ;
    static {
        try {
            //1. Load configuration file
            Properties pro = new Properties();
            InputStream resourceAsStream = DruidDemo.class.getClassLoader().getResourceAsStream("druid.properties");
            pro.load(resourceAsStream);
            //2. Get DataSource
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**
     * Get resources
     * @return
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        return  ds.getConnection();
    }

    /**
     * Release resources
     * @param conn
     * @throws SQLException
     */
    public static void close(Statement stmt, Connection conn) throws SQLException {

        close(null,stmt,conn);
        //Method overload, call the following method
    }

    public static void close(ResultSet rs, Statement stmt, Connection conn) throws SQLException {
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if(stmt != null){
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if(conn != null){
            try {
                conn.close();//Return connection
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Get connection pool method
     */
    public static DataSource getDataSource(){
        return ds;
    }

}

5. Create the package cn.itcast.dao, create the class UserDao, and provide the login method

package dao;

import User.User;
import druid.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

import java.sql.SQLException;

public class UserDao {
    private JdbcTemplate jdbcTemplate = new JdbcTemplate(JDBCUtils.getDataSource());
    public User login(User loginUser){
        try {
            //Write sql
            String sql = "select * from user where username = ? and password = ?";
            //Call the query method
            User user = jdbcTemplate.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), loginUser.getUsername(), loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {
            e.printStackTrace();//Log
            return null;
        }
    }

}

1. Write cn.itcast.web.servlet.LoginServlet class

package servlet;

import User.User;
import dao.UserDao;

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("/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //Set encoding
        req.setCharacterEncoding("utf-8");
        //Get request parameters
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //Encapsulate user object
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        //Call the login method of UserDao
        UserDao userDao = new UserDao();
        User login = userDao.login(user);

        if(user == null){
            //Login failed
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        }else {
            req.setAttribute("user",user);
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }
    }
}

1. Write FailServlet and SuccessServlet classes

failServlet.java

package servlet;

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("/failServlet")
public class failServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");
        //output
        resp.getWriter().write("Login failed, wrong user name or password");
    }
}

successServlet.java

package servlet;

import User.User;

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("/successServlet")
public class successServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        User user = (User)req.getAttribute("user");
        if (user!=null){
            resp.setContentType("text/html;charset=utf-8");
            resp.getWriter().write("Login successful"+user.getUsername()+"，Welcome");
        }
    }

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

1. How to write the action path of form in login.html

   • Resource path of virtual directory + Servlet

2. BeanUtils tool class to simplify data encapsulation

Import BeanUtils jar package

Because every time we need to get a parameter, we have to req.getParameter to increase the amount of code.

code:

//        //Get request parameters
//        String username = req.getParameter("username");
//        String password = req.getParameter("password");
//        //Encapsulate user object
//        User userlogin = new User();
//        userlogin.setUsername(username);
//        userlogin.setPassword(password);

        //Get request parameters
        Map<String, String[]> parameterMap = req.getParameterMap();
        User userlogin = new User();
        
        //encapsulation
        try {
            BeanUtils.populate(userlogin,parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

BeanUtils is used to encapsulate JavaBean s

JavaBean s: standard Java classes

			1. requirement:
				1. Class must be public modification
				2. Constructor that must provide null arguments
				3. Member variables must use private modification
				4. Provide public setter and getter method
			2. Function: encapsulate data

Concept:

			Member variables:
			Properties: setter and getter Method intercepted product
				For example: getUsername() --> Username--> username

method:

			1. setProperty()
			2. getProperty()
			3. populate(Object obj , Map map):take map The key value pair information of the collection is encapsulated into the corresponding JavaBean Object

It operates on an attribute, not a member variable

getUsername() --> Username–> username