Request

Get request data

I Request inheritance system

RequestFacade ------> HttpServletRequest ------> ServletRequest

ServletRequest: the root interface of the request object provided by Java

HttpServletRequest: the request object interface encapsulated by HTTP protocol provided by Java

RequestFacade: implementation class defined by Tomcat

• Tomcat needs to parse the request data, encapsulate it as a request object, and create a request object to pass to the service method

• Use the request object to consult the HttpServletRequest interface of the Java EE API document

II Request get request data

1. Get request data

01. Request line

GET /request-demo/req1?username=zhangsan HTTP/1.1 

Case:

localhost:8080/web-demo01/req1?username=zhangsan&password=123

        /**
         * Method: String getMethod()
         * Result: method = GET
         */
        String method = req.getMethod();
        System.out.println("method = " + method);
        
        /**
         * Method: String getContextPath()
         * Result: contextPath = /web-demo01
         */
        String contextPath = req.getContextPath();
        System.out.println("contextPath = " + contextPath);
        
        /**
         * Method: StringBuffer getRequestURL()
         * Result: requesturl= http://localhost:8080/web -demo01/req1
         */
        StringBuffer requestURL = req.getRequestURL();
        System.out.println("requestURL = " + requestURL);
        
        /**
         * Method: String getRequestURI()
         * Result: requestURI = /web-demo01/req1
         */
        String requestURI = req.getRequestURI();
        System.out.println("requestURI = " + requestURI);

        /**
         * Method: String getQueryString()
         * Result: querystring = username = Zhangsan & password = 123
         */
        String queryString = req.getQueryString();
        System.out.println("queryString = " + queryString);

02. Request header

User-Agent: Mozilla/5.0 Chrome/91.0.4472.106

/**
 * Get request header
 * user-agent: Browser version information
 * Result: header = Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36 Edg/101.0.1210.47
 */
String header = req.getHeader("user-agent");
System.out.println("header = " + header);

03. Requestor

Only POST mode is available

username=superbaby&password=123

/**
 * Get post request body
 * Result: line = username = Zhangsan & password = 123
 */
//1. Get character input stream
BufferedReader br = req.getReader();
//2. Read data
String line = br.readLine();
System.out.println("line = " + line);

2. Obtain request parameters in a general way

Just write one, regardless of whether it uses the GET or POST method

<form action="/web-demo01/req2" method="post">
    <input type="text" name="username"><br>
    <input type="password" name="password"><br>
    <input type="checkbox" name="hobby" value="1">Swimming
    <input type="checkbox" name="hobby" value="2">Mountain climbing<br>
    <input type="submit">
</form>

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    //1. Get the map set of all parameters
    Map<String, String[]> map = req.getParameterMap();
    for (String key : map.keySet()) {
        System.out.print(key+":");
        String[] values = map.get(key);
        for (String value : values) {
            System.out.print(value+" ");
        }
        System.out.println();
    }
    System.out.println("--------------------");

    //2. Get the parameter value according to the key and the array
    String[] hobbies = req.getParameterValues("hobby");
    for (String hobby : hobbies) {
        System.out.println(hobby);
    }

    //3. Obtain a single parameter value according to the key
    String username = req.getParameter("username");
    String password = req.getParameter("password");
    System.out.println("username = " + username);
    System.out.println("password = " + password);
}

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

    this.doGet(req, resp);
}

Console:

username:admin
password:123456

hobby:1 2

1
2
username = admin
password = 123456

3. Chinese garbled code of request parameters

01.POST mode

//Set POST mode garbled code
request.setCharacterEncoding("UTF-8");

02.GET method

String username = request.getParameter("username");
String username1 = new String(username.getBytes("ISO-8859-1"),"UTF-8");
System.out.println("username1 = " + username1);

3, Request forwarding

A resource jump mode inside the server

Sender:

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("demo5");

    request.setAttribute("msg","hello");

    //Request forwarding
    request.getRequestDispatcher("/req6").forward(request,response);
}

Receiving end:

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("demo6");

    Object msg = request.getAttribute("msg");
    System.out.println("msg = " + msg);
}

**Implementation method: * * req Getrequestdispatcher ("resource B path") forward(request,response);

Request forwarding features:

• The browser address bar path does not change

• It can only be forwarded to the internal resources of the current server

• For one request, you can use request to share data among the forwarded resources

Response

Use the response object to set the response data

1, Response architecture

ResponseFacade ------> HttpServletResponse ------> ServletResponse

ServletResponse: the root interface of the request object provided by Java

HttpServletResponse: the request object encapsulated by the Http protocol provided by Java

ResponseFacade: implementation class defined by Tomcat

2, Response set response data function

The response data is divided into three parts

1. Response line:

HTTP/1.1 200 OK

2. Response head

Content-Type: text/html

3. Responder

<html><head>head><body></body></html>

3, Response complete redirection

A resource jump mode

Resource A said to the browser that I can't handle this. Find someone else (status code) to handle it. The person's location is XXX (response header location:xxx)

Implementation method:

resp.setStatus(302);
resp. Path of setheader ("set location");

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //redirect
    //1. Set the response status code 302
    response.setStatus(302);
    //2. Set the response header Location
    response.setHeader("Location","/web-demo01//resp2");
}

Simplified implementation:

resp.sendRedirect("path of resource B");

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //Simplify redirection
    response.sendRedirect("/web-demo01//resp2");
}

Redirection features:

• The browser address bar path does not change

• It can only be forwarded to the internal resources of the current server

• For one request, you can use request to share data among the forwarded resources

Path resource problem

• Specify who uses the path?

  • Browser usage: need to add virtual directory
  • Server use: no need to add virtual directory

• Dynamic path:

String contextPath = request.getContextPath();
response.sendRedirect(contextPath + "/resp2");

4, Response response character data

• use

​ 1. Get the character output stream through the Response object

​ PrintWriter writer = resp.getWriter();

​ 2. Write data

​ writer.write("aaa");

• details

  1. The flow does not need to be closed. With the end of the response, the response object is destroyed and closed by the server

​ 2. Chinese data garbled: Reason: the default code of the character output stream obtained through the Response is ISO-8859-1

​ resp.setContentType("text/html;charset=utf-8");

//It simplifies html parsing and character formatting
response.setContentType("text/html;charset=utf-8");
//1. Get character output stream
PrintWriter writer = response.getWriter();

//Content type setting html parsing
//response.setHeader("content-type","text/html");

writer.write("<h1>Hello</h1>");

After opening, the web page is a h1 label with the word "hello"

5, Response response byte data

• use

  1. Get byte output stream through Response object

​ ServletOutputStream outputStream = resp.getOutputStream();

​ 2. Write data

​ outputStream. Write (byte data);

• troublesome!!!

//1. Read the file
FileInputStream fis = new FileInputStream("C:\\Users\\Liu Hao\\Desktop\\07.jpg");
//2. Get the response byte output stream
ServletOutputStream os = response.getOutputStream();
//3. Complete the copy of the stream
byte[] buff = new byte[1024];
int len = 0;
while ((len = fis.read(buff)) != -1){
    os.write(buff,0,len);
}
fis.close();

• IOUtils tool class

<dependency>
  <groupId>commons-io</groupId>
  <artifactId>commons-io</artifactId>
  <version>2.6</version>
</dependency>

• After simplification

//1. Read the file
FileInputStream fis = new FileInputStream("C:\\Users\\Liu Hao\\Desktop\\07.jpg");
//2. Get the response byte output stream
ServletOutputStream os = response.getOutputStream();
//3. Complete the copy of the stream
IOUtils.copy(fis,os);
fis.close();

6, User login and registration function cases

UserMapper

public interface UserMapper {

    /**
     * Query user objects by user name and password
     * @param username
     * @param password
     * @return
     */
    @Select("select * from tb_user where username = #{username} and password = #{password}")
    User select(@Param("username") String username, @Param("password") String password);

    /**
     * Query user object by user name
     * @param username
     * @return
     */
    @Select("select * from tb_user where username = #{username}")
    User selectByUsername(@Param("username") String username);

    @Insert("insert into tb_user values(null,#{username},#{password})")
    void add(User user);
}

RegisterServlet

@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. Accept user data
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        //Encapsulate user objects
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        //2. Call mybatis to complete the query
        //2.1 get sqlSessionFactory object
//        String resource = "mybatis-config.xml";
//        InputStream inputStream = Resources.getResourceAsStream(resource);
//        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryUtils.getSqlSessionFactory();
        //2.2 get sqlSession object
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //2.3 get Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        //2.4 calling method
        User u = userMapper.selectByUsername(username);

        //3. Judge whether the user exists
        if (u == null){
            //user name does not exist
            userMapper.add(user);
            //Commit transaction
            sqlSession.commit();
            //Release resources
            sqlSession.close();
        }else {
            //User name exists
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("User name already exists");
        }

    }

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

LoginServlet

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. Accept user name and password
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        //2. Call mybatis to complete the query
        //2.1 get sqlSessionFactory object
//        String resource = "mybatis-config.xml";
//        InputStream inputStream = Resources.getResourceAsStream(resource);
//        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryUtils.getSqlSessionFactory();
        //2.2 get sqlSession object
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //2.3 get Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        //2.4 calling method
        User user = userMapper.select(username, password);
        //2.5 releasing resources
        sqlSession.close();

        //Get the character output stream and set the content type
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        //3. Judge whether user is null
        if (user != null){
            writer.write("Login successful");
        }else {
            writer.write("Login failed");
        }
    }

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

Interface

<form action="/web-demo01/loginServlet" id="form" method="post">
    <h1 id="loginMsg">LOGIN IN</h1>
    <p>Username:<input id="username" name="username" type="text"></p>

    <p>Password:<input id="password" name="password" type="password"></p>

    <div id="subDiv">
        <input type="submit" class="button" value="login up">
        <input type="reset" class="button" value="reset">&nbsp;&nbsp;&nbsp;
        <a href="register.html">No account? Click Register</a>
    </div>
</form>

<body>

<div class="form-div">
    <div class="reg-content">
        <h1>Welcome to register</h1>
        <span>Existing account?</span> <a href="login.html">Sign in</a>
    </div>
    <form id="reg-form" action="/web-demo01/registerServlet" method="post">

        <table>

            <tr>
                <td>user name</td>
                <td class="inputs">
                    <input name="username" type="text" id="username">
                    <br>
                    <span id="username_err" class="err_msg" style="display: none">User names are not very popular</span>
                </td>

            </tr>

            <tr>
                <td>password</td>
                <td class="inputs">
                    <input name="password" type="password" id="password">
                    <br>
                    <span id="password_err" class="err_msg" style="display: none">Incorrect password format</span>
                </td>
            </tr>


        </table>

        <div class="buttons">
            <input value="Register" type="submit" id="reg_btn">
        </div>
        <br class="clear">
    </form>

</div>
</body>

sqlSessionFactoryUtils optimization

public class sqlSessionFactoryUtils {

    private static SqlSessionFactory sqlSessionFactory;

    //Static code blocks are loaded only once
    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }


    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }
}

Call direct later

SqlSessionFactory sqlSessionFactory = sqlSessionFactoryUtils.getSqlSessionFactory();