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Java é um aplicativo da web simples. Login e registro

Bom Dia a todos.


Este artigo é destinado a iniciantes no mundo da Web e Java. Examinaremos a arquitetura padrão de aplicativos da web e faremos um pequeno projeto do zero.


Usaremos o Spring (Huge Web Framework), mas no mínimo. Se você não tem experiência anterior no uso e tenta usar imediatamente toda a funcionalidade, não haverá entendimento básico, pois há uma lista de armadilhas.


O que o aplicativo fará?


Quero apresentar um exemplo curto e ao mesmo tempo útil. Ele é minimamente carregado e, no final, você pode usá-lo como modelo.


Pensando no que as pessoas geralmente enfrentam ao desenvolver um aplicativo da Web, percebi que a implementação do login e do registro será bastante reveladora e útil.


Você pode encontrar o código fonte aqui .


O que vamos usar


  • IDE favorito (eu uso o IntelliJ IDEA)
  • cabeça não nublada
  • Maven (construtor de projetos)
  • JDBC (o link entre Java e DBMS)

Criação de projeto


Crie um projeto Maven simples. Fazemos tudo do zero, sem adicionar nenhum arquétipo.
O IDE deve gerar essa estrutura.


imagem


E então o que vemos.


  • java - o principal local onde a "mágica" ocorrerá
  • resources — . ( , , front )
  • test — . ( , )
  • pom.xml — Maven. , , "" .

, IDE, - Maven.


imagem


-


, .
, .


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-, , "-".


.


  1. Browser — . Frontend. Backend — , . .
  2. Controller — Frontend, . , , .
  3. Service — - . . .
  4. DAL(data access layer) — . , , , .
  5. Database — , .


- .


, H2.


, -. User.


create table DATABASE.USER
(
    ID INT auto_increment,
    NAME VARCHAR not null,
    SURNAME VARCHAR not null,
    LOGIN VARCHAR not null,
    PASSWORD VARCHAR not null,
    constraint USER_PK
        primary key (ID)
);

Spring


java.


java com.zuk( ), App main .


Spring. , @SpringBootApplication Spring, , . Spring .


//com.zuk.App
@SpringBootApplication
public class App {

    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

pom.xml.


<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.zuk</groupId>
    <artifactId>LoginAndRegistration</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.2.5.RELEASE</version>
        </dependency>
    </dependencies>

</project>

, Spring .


imagem


Spring 8080. , http://localhost:8080.



, Spring , .


application.properties src.main.resources.


-.


spring.datasource.driverClassName=org.h2.Driver
spring.datasource.url=jdbc:h2:~/test

spring.datasource.username=sa
spring.datasource.password=

Spring, .


, .
, . , . Spring .
.


java.com.zuk.connection ConnectionManager, , .
properties, FileInputStream.


//ConnectionManager
FileInputStream fis;
Properties property = new Properties();

application.properties, properties.


//ConnectionManager
fis = new FileInputStream("src/main/resources/application.properties");
property.load(fis);

getConnection.


  //ConnectionManager
  public Connection getConnection() {
            Connection connection = null;
            try {
                connection = DriverManager.getConnection(property.getProperty("spring.datasource.url"),property.getProperty("spring.datasource.username"),property.getProperty("spring.datasource.password"));
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return connection;
        }

, App.


, .


conn2: url=jdbc:h2:~/test user=SA

, pom.


<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <version>1.4.200</version>
</dependency>

POJO (Plain Old Java Objects)


, , .


, , . , , , . , , . POJO.


, User.
.


java.com.zuk.entity, User.
, .


User.java
public class User {

    private int id;
    private String name;
    private String surname;
    private String login;
    private String password;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSurname() {
        return surname;
    }

    public void setSurname(String surname) {
        this.surname = surname;
    }

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getPassword() {
        return password;
    }

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

}

DAL


, , DAL. , . DAO (data access object) — - .


java.com.zuk.dao UserDao ( ). findByLogin, save.


public interface UserDao {
    User findByLogin(String login);
    Boolean save(User user);
}

, java.com.zuk.dao.impl,
UserDaoImpl.
— , , (, ).


public class UserDaoImpl implements UserDao {
    @Override
    public User findByLogin(String login) {
        return null;
    }

    @Override
    public Boolean save(User user) {
        return null;
    }
}

findByLogin. SQL .


SELECT  * from DATABASE.User where LOGIN=login

User.


, null.


//UserDaoImpl
ConnectionManager cm = new ConnectionManager();
Connection con = cm.getConnection();

@Override
    public User findByLogin(String login) {
        User user = null;
        if (con != null) {
              //..  
        }
        return user;
     }

if , SQL , user.


//findByLogin
PreparedStatement pr = con.prepareStatement("SELECT * FROM DATABASE.User where LOGIN=?");
pr.setString(1 , login);
ResultSet resultSet = pr.executeQuery();//return sql result
if(resultSet.next()) {
       user = new User();
       user.setId(resultSet.getInt("ID"));
       user.setName(resultSet.getString("NAME"));
       user.setSurname(resultSet.getString("SURNAME"));
       user.setLogin(login);
       user.setPassword(resultSet.getString("PASSWORD"));
       return user;
}
 pr.close();
 con.close();

.


save .
.


save
//UserDaoImpl
@Override
    public Boolean save(User user) {
        ConnectionManager cm = new ConnectionManager();
        Connection con = cm.getConnection();
        if (con != null) {
            try {
                PreparedStatement pr = con.prepareStatement("insert into DATABASE.USER (NAME,SURNAME,LOGIN,PASSWORD) values (?,?,?,?)");
                pr.setString(1,user.getName());
                pr.setString(2,user.getSurname());
                pr.setString(3,user.getLogin());
                pr.setString(4, DigestUtils.md5DigestAsHex((user.getPassword()).getBytes()));
                pr.executeUpdate();
                pr.close();
                con.close();
                return true;
            } catch (SQLException e) {
                e.printStackTrace();

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return false;
    }

Service


-. java.com.zuk.service, UserService : login, registration. UserServiceImpl java.com.zuk.service.impl, UserService.


public class UserServiceImpl implements UserService {
    @Override
    public String login(User user) {
        return null;
    }

    @Override
    public String registration(User user) {
        return null;
    }
}

login.
:


  1. "login" .
  2. 1 , .
  3. 2 , "life is beautiful"

//UserServiceImpl
UserDaoImpl userDao = new UserDaoImpl();
    @Override
    public String login(User user) {
        User findUser = userDao.findByLogin(user.getLogin());
        if(findUser!=null){
            if(DigestUtils.md5DigestAsHex((user.getPassword()).getBytes()).equals(findUser.getPassword())){
                return "life is beautiful"  + "your Id: " + findUser.getId();
            }
        }
        return "do not give up";
    }

.


registration
 @Override
    public String registration(User user) {
        User findUser = userDao.findByLogin(user.getLogin());
        if(findUser==null) {
            userDao.save(user);
            return "life is beautiful";
        }
        return "this login is not available";
    }

Controller


, - .
java.com.zuk.controller Controller. "" RestController, Spring , Rest Controller.
, @RequestMapping("/").


@RestController
public class Controller {
    @RequestMapping("/")
    String main() {
        return "Hello from Controller";
    }
}

, http://localhost:8080.
"Hello from Controller".


html . , .
resources, resources.static.


html
<!--loginFrom.html-->
<html>
<title>Login</title>
<body>
<form action="http://localhost:8080/login"  method="post">
    <input type="text" required name="login" placeholder="login" />
    <input type="password" required name="password" placeholder="password" />
    <button>login</button>
</form>
<a href="http://localhost:8080/registrationForm">don't have account</a>
</body>
</html>

<!--registrationForm.html-->
<html>
<title>Registration</title>
<body>
<form action="http://localhost:8080/registration"  method="post">
    <input type="text" required name="name" placeholder="name" />
    <input type="text" required name="surname" placeholder="surname" />
    <input type="text" required name="login" placeholder="login" />
    <input type="password" required name="password" placeholder="password" />
    <button>registration</button>
</form>
<a href="http://localhost:8080/loginForm">already have account</a>
</body>
</html>

, http://localhost:8080/loginForm, http://localhost:8080/registrationForm html .
, /loginForm, /registrationForm html. ModelAndView.


//Controller
 @RequestMapping("/loginForm")
    ModelAndView loginForm() {
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("loginForm.html");
        return modelAndView;
    }

    @RequestMapping("/registrationForm")
    ModelAndView registrationForm() {
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("registrationForm.html");
        return modelAndView;
    }

, action http://localhost:8080/login registration, .
service.


//Controller
UserServiceImpl userService = new UserServiceImpl();
//..
 @PostMapping("/login")
    String login(@RequestParam String login,@RequestParam String password) {
        User user = new User();
        user.setLogin(login);
        user.setPassword(password);
        return userService.login(user);
    }

    @PostMapping("/registration")
    String registration(@RequestParam String name,@RequestParam String surname, @RequestParam String login,@RequestParam String password) {
        User user = new User();
        user.setName(name);
        user.setSurname(surname);
        user.setLogin(login);
        user.setPassword(password);
        return userService.registration(user);
    }

Vemos que nossos métodos no Controller começaram a aceitar parâmetros. Estes são os parâmetros que escrevemos em nossos formulários. Seus nomes devem corresponder à entrada de nomes.


Conclusão


Espero que este artigo tenha sido capaz de responder a algumas de suas perguntas e tenha ajudado a expandir seus horizontes.


Tudo um desenvolvimento agradável.

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