SpringBoot framework basics

1. SpringBoot framework

The SpringBoot framework can be simply understood as “an enhanced Version of the SpringMVC framework, which greatly simplifies configuration and integrates most common dependencies by default”.

2. How to create a SpringBoot project

3. Create a SpringBoot project

Go to https://start.spring.io and confirm the following parameters:

• [Project] : Maven Project
• [Language] : Java
• [SpringBoot] : 2.1.14
• [Group] : cn. Tedu
• Artifact: Sample
• [Name] : sample
• [Package Name] : cn.tedu.sample
• 【Packaging】 : War
• [Java] : 8
• 【Dependencies】 : None

After you are sure, click the Generate button in the page, the automatic download will start, and you will get the sample.zip package.

Decompress sample.zip to obtain the sample folder. This folder is the created SpringBoot project.

Maven Projects: Import > Existing Maven Projects: Import > Existing Maven Projects: Import > Existing Maven Projects: Import > Existing Maven Projects: Import > Existing Maven Projects: Import > Existing Maven Projects You can connect to the Maven server without any problems. If automatic downloads are not started, you can right click on the Project and choose Maven > Update Project to Update the Project, or even force the Project to Update.

Note: Depending on the plug-in installed by the development tool, there may be some additional branches or ICONS in the project structure that do not affect normal development and operation.

Note: If you are using a lower version of Eclipse, you may have built in a lower version of Maven environment. After creating a SpringBoot project, the pom.xml file may report an error, but it can be ignored and does not affect development and operation.

4. Start the SpringBoot project

5. Add static resources to the project

Static resources: web page files (.html files), image files,.CSS files,.js files, on the server, can be directly requested by the client files.

In the SpringBoot project, under SRC /main/resources, there is a static folder by default, which is used to store static resources!

In fact, static resources can also be placed in the webApp folder of your project. SpringBoot recommends that static resources be placed under Static.

The index. HTML file can be created static, and the contents of the file can be arbitrarily designed.

Then, start the project, open a browser, type in the url http://localhost:8080 to see your own design of the web page.

The following log appears in the console when the project is started:

Tomcat started on port(s): 8080 (http) with context path ''
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As you can see, internal Tomcat sets the context path value to an empty string when deploying the current project, so there is no need to add the project name to the URL accessing the project!

Since this attempt to access the resource is index.html, is the default resource name, so, there is no need to explicitly add the resource name in the URL!

In a SpringBoot project, under SRC /main/resources, there is an application. Properties file by default, which is the configuration file for the project.

You can modify the ports used by Tomcat in the configuration file. You need to add the following configuration:

server.port=80
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Because port 80 is the default HTTP port, when changed to port 80, restart the project (stop first, then start), in the browser through http://localhost to access the previous web page!

Note: If you use Linux or Unix derived operating systems such as Mac OS, these operating systems strictly manage the port number. By default, you cannot change the port number to 80 unless you set the port number to 80 in the operating system.

6. Use the controller to receive requests from clients

package cn.tedu.sample.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloController {
	
	@RequestMapping("hello")
    @ResponseBody
	public String hello(a) {
		return "SpringBoot is so good!!"; }}Copy the code

7. Connect to the database

By default, the SpringBoot project does not have jar packages that integrate the database and database programming framework. You need to check the relevant dependencies when creating the project, or add the relevant code to the pop.xml after creating the project:

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.2</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>
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For example, mysql-connector-java does not specify a version number. For example, mysql-connector-java does not specify a version number. Of course, if you must use a particular version, you can add your own

node for configuration, and use the specified version!

Once the above dependencies are added, when the project is started, the configuration information for connecting to the database will be automatically loaded. If it is not configured, the startup will fail! Therefore, you must add a configuration in application.properties:

spring.datasource.url=jdbc:mysql://localhost:3306/tedu_ums? useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai spring.datasource.username=root spring.datasource.password=rootCopy the code

When you add the above configuration, SpringBoot will not fail to start again, even if the above configuration information is incorrect! Because the project will only “load information”, not “direct database”, so, above configuration, as long as the basic format is correct!

You can write unit tests under SRC /test/ Java to try to connect to the database to check that the above configuration information is correct! Add the following code to the SampleApplicationTests class in the cn.tedu.sample package:

@Autowired
public DataSource dataSource;

@Test
public void getConnection(a) throws SQLException {
    Connection conn = dataSource.getConnection();
    System.err.println(conn); // Err is only used to output red logs for easy observation.
}
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When programming with the SpringBoot framework, any object that can be obtained with getBean() in traditional SSM frameworks can be assembled by adding auto-assembly annotations!

8. Realize database programming with MyBatis

public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    private String phone;
    private String email;
}
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Integer addnew(User user);
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<! DOCTYPEmapper
  PUBLIC "- / / mybatis.org//DTD Mapper / 3.0 / EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
  
<mapper namespace="cn.tedu.sample.mapper.UserMapper">

	<insert id="addnew">
		INSERT INTO t_user (
			username, password, age, phone, email
		) VALUES (
			#{username}, #{password}, #{age}, #{phone}, #{email}
		)
	</insert>

</mapper>
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mybatis.mapper-locations=classpath:mappers/*.xml
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package cn.tedu.sample.mapper;

import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTests {}Copy the code

package cn.tedu.sample.mapper;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import cn.tedu.sample.entity.User;

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTests {
	
	@Autowired
	public UserMapper userMapper;
	
	@Test
	public void addnew(a) {
		User user = new User();
		user.setUsername("SpringBoot");
		user.setPassword("1234");
		user.setAge(28);
		user.setPhone("13900139008");
		user.setEmail("[email protected]");
		Integer rows = userMapper.addnew(user);
		System.err.println("rows="+ rows); }}Copy the code

[Target] Query user data based on the user name

SQL statements that need to be executed are as follows:

select * from t_user where username=?
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Add an abstract method to the UserMapper interface:

User findByUsername(String username);
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And configure the mapping in usermapper.xml:

<select id="findByUsername" resultType="cn.tedu.sample.entity.User">
	SELECT * FROM t_user WHERE username=#{username}
</select>
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When complete, write and execute unit tests in UserMapperTests:

@Test
public void findByUsername(a) {
    String username = "test";
    User user = userMapper.findByUsername(username);
    System.err.println(user);
}
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9. Complete the user registration function

When the user tries to register, the user will fill in the registration information in the page, and then click the button to submit the request! The request will be received by the controller on the server side, but the controller is not responsible for adding, deleting, modifying, and checking the data, so it will be handed over to UserMapper for execution!

Next, we need to develop the functionality of the controller by creating the util sub-package under cn.tedu.sample and creating the usual JSON result type in this package:

public class JsonResult<T> {
    private Integer state;
    private String message;
    private T data;
}
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In cn. Tedu. Sample. The controller package created in UserController controller class, before the declaration of a class to add @ RestController and @ RequestMapping annotations (” user “), and declare the persistence layer objects:

@RestController
@RequestMapping("user")
public class UserController {
    @Autowired
    private UserMapper userMapper;
}
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Then, add a method to the class to handle the “register” request:

// http://localhost/user/reg? username=jsd2020&password=5678&age=19&phone=13700137777&[email protected]
@RequestMapping("reg")
public JsonResult<Void> reg(User user) {
    // Prepare the return value object
    JsonResult<Void> jsonResult = new JsonResult<Void>();
    // Query the database based on username in the user parameter
    User result = userMapper.findByUsername(user.getUsername());
    // Check whether the query result is null
    if (result == null) {
        // If no matching data is found, the user name is not occupied and registration is allowed
        userMapper.addnew(user);
        jsonResult.setState(1);
    } else {
        // No: If matching data is found, the user name has been occupied and registration is not allowed
        jsonResult.setState(2);
        jsonResult.setMessage("Registration failed! The user name you tried to register is already in use!");
    }
    / / return
    return jsonResult;
}
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When you’re done, restart the project and open your browser to test by typing in the url.

Create an asynchronous request to the server using Ajax, and process the result:

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