spring boot入门例子

2022-07-13 17:03:54

最近学习spring boot，总结一下入门的的基础知识

1新建maven项目，修改pom.xml

<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/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>

  <groupId>cn.sam</groupId>

  <artifactId>springboot3</artifactId>

  <packaging>war</packaging>

  <version>0.0.1-SNAPSHOT</version>

  <name>springboot3 Maven Webapp</name>

  <url>http://maven.apache.org</url>

      <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <!-- 这里一定要配置上java的版本，如果是1.7版本的可不用配置 -->

        <java.version>1.8</java.version>

    </properties>

<parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>1.4.1.RELEASE</version>

    <relativePath/>

  </parent>

  <dependencies>

    <dependency>

      <groupId>org.springframework.boot</groupId>

      <artifactId>spring-boot-starter-web</artifactId>

    </dependency>

  </dependencies>

  <build>

    <plugins>

      <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

      </plugin>

    </plugins>

  </build>

</project>

2新建main类如下，运行main方法，然后在浏览器输入http://127.0.0.1:8080/hello

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

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

import org.springframework.web.bind.annotation.RestController;

@RestController

@EnableAutoConfiguration

public class Application {

	public static void main(String[] args) {

		SpringApplication.run(Application.class, args);

	}

	@RequestMapping("/hello")

	public String hello(){

		return "Hello World!";

	}

}

这样一个简单的入门例子就完成了，是不是非常的简单呢。

下面记录一下spring boot的一些简单配置

1在我们开发过程中，我们需要经常修改，为了避免重复启动项目，我们可以启用热部署。

Spring-Loaded项目提供了强大的热部署功能，添加/删除/修改方法/字段/接口/枚举等代码的时候都可以热部署，速度很快，很方便。想在Spring Boot中使用该功能非常简单，就是在spring-boot-maven-plugin插件下面添加依赖：

<dependencies>

    <dependency>

        <groupId>org.springframework</groupId>

        <artifactId>springloaded</artifactId>

        <version>1.2.5.RELEASE</version>

    </dependency>

</dependencies>

添加以后，用cmd进入项目目录，通过mvn spring-boot:run启动就支持热部署了(这里是用mvn命令去启动项目，并不是运行main方法)。

2修改服务器端口

一main方法类实现EmbeddedServletContainerCustomizer接口

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;

import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;

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

import org.springframework.web.bind.annotation.RestController;

@RestController

@EnableAutoConfiguration

public class Application1 implements EmbeddedServletContainerCustomizer {

	@Override

	public void customize(ConfigurableEmbeddedServletContainer container) {

		container.setPort(8899);

	}

	public static void main(String[] args) {

		SpringApplication.run(Application1.class, args);

	}

	@RequestMapping("/hello")

	public String port(){

		return "port 8899";

	}

}

二主类添加一个factory方法

import java.util.concurrent.TimeUnit;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;

import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;

import org.springframework.context.annotation.Bean;

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

import org.springframework.web.bind.annotation.RestController;

@RestController

@EnableAutoConfiguration

public class Application2 {

	public static void main(String[] args) {

		SpringApplication.run(Application2.class, args);

	}

	@RequestMapping("/hello")

	public String hello(){

		return "port 8890";

	}

	@Bean

    public EmbeddedServletContainerFactory servletFactory(){

        TomcatEmbeddedServletContainerFactory tomcatFactory = new TomcatEmbeddedServletContainerFactory();

        tomcatFactory.setPort(8890);

        tomcatFactory.setSessionTimeout(10,TimeUnit.SECONDS);

        return tomcatFactory;

    }

}

Hello World例子只是一个controller，可以在主类增加扫描，实现多个controller

1新建User实体类

public class User {

	private Integer id;

	private String name;

	public Integer getId() {

		return id;

	}

	public void setId(Integer id) {

		this.id = id;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

}

2新建UserController

import org.springframework.web.bind.annotation.PathVariable;

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

import org.springframework.web.bind.annotation.RestController;

import springboot3.domain.User;

@RequestMapping("/user")

@RestController

public class UserController {

	@RequestMapping("/{id}")

	public User getUserById(@PathVariable String id){

		User u = new User();

		u.setId(new Integer(id));

		u.setName("name="+id);

		return u;

	}

}

3新建DepartmentController

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

import org.springframework.web.bind.annotation.RestController;

@RequestMapping("/dep")

@RestController

public class DepartmentController {

	@RequestMapping("name")

	public String getDepName(){

		return "Dep name.";

	}

}

4新建主类

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

import org.springframework.context.annotation.ComponentScan;

@EnableAutoConfiguration

@ComponentScan(value = {"springboot3.controller"})

public class Application4 {

	public static void main(String[] args) {

		SpringApplication.run(Application4.class, args);

	}

}

运行主方法，在浏览器输入http://127.0.0.1:8080/user/1

在浏览器输入http://127.0.0.1:8080/user/1

上面例子中，user用到url中的变量，可以直接获取

@RequestMapping("/users/{username}")

public String userProfile(@PathVariable("username") String username) {

    return String.format("user %s", username);

}

@RequestMapping("/posts/{id}")

public String post(@PathVariable("id") int id) {

    return String.format("post %d", id);

}

支持http方法

@RequestMapping(value = "/login", method = RequestMethod.GET)

public String loginGet() {

    return "Login Page";

}

@RequestMapping(value = "/login", method = RequestMethod.POST)

public String loginPost() {

    return "Login Post Request";

}

上面的例子，为了方便演示，都是采用restcontroller，spring boot也可以用模板

我们使用Thymeleaf模板引擎进行模板渲染，需要引入依赖：

<dependency>

  <groupId>org.springframework.boot</groupId>

  <artifactId>spring-boot-starter-thymeleaf</artifactId>

</dependency>

controller类

@Controller

public class HtmlController {

	@RequestMapping("/html/{name}")

	public String html(@PathVariable("name") String name, Model model){

		model.addAttribute("name","Hello Html "+name);

		return "html";

	}

}

接下来需要在默认的模板文件夹src/main/resources/templates/目录下添加一个模板文件hello.html

<html xmlns:th="http://www.thymeleaf.org">

<head>

    <title>Getting Started: Serving Web Content</title>

    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

</head>

<body>

    <p th:text="'Hello, ' + ${name} + '!'" />

</body>

</html>

访问http://127.0.0.1:8080/html/sam

浏览器页面使用HTML作为描述语言，那么必然也脱离不了CSS以及JavaScript。为了能够浏览器能够正确加载类似/css/style.css, /js/main.js等资源，默认情况下我们只需要在src/main/resources/static目录下添加css/style.css和js/main.js文件后，Spring MVC能够自动将他们发布，通过访问/css/style.css, /js/main.js也就可以正确加载这些资源。

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