spring-boot官网入门指导

系统需求

spring boot 2.0需要 jdk1.8 、spring5.0+，maven 3.2+ 或者gradle 4

使用 Maven安装spring boot

Spring Boot dependencies use the org.springframework.boot groupId. Typically your Maven POM file will inherit from the spring-boot-starter-parent project and declare dependencies to one or more “Starters”. Spring Boot also provides an optional Maven plugin to create executable jars.

spring boot依赖使用org.springframework.boot groupId.一般的话，你的maven pom.xml文件会继承于spring-boot-starter-parent 工程。Spring Boot也提供了一个可选的maven 插件用于创建可执行jars包。

一般来说，pom.xml文件会是这样的：

<?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>com.example</groupId>
    <artifactId>myproject</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <!-- Inherit defaults from Spring Boot -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.BUILD-SNAPSHOT</version>
    </parent>

    <!-- Add typical dependencies for a web application -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <!-- Package as an executable jar -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <!-- Add Spring repositories -->
    <!-- (you don't need this if you are using a .RELEASE version) -->
    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
            <snapshots><enabled>true</enabled></snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </pluginRepository>
    </pluginRepositories>
</project>

安装sprin boot cli脚手架

下载地址

Once downloaded, follow the INSTALL.txt instructions from the unpacked archive. In summary: there is a spring script (spring.bat for Windows) in a bin/ directory in the .zip file

下载后，打开install.txt按照说明安装。可以双击spring.bat文件，然后打开shell 敲入 spring --version看是否安装成功。若没有，可配置一下环境变量后再测试一遍。

第一个Spring Boot 程序

1. 创建pom.xml文件

<?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>com.example</groupId>
    <artifactId>myproject</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.BUILD-SNAPSHOT</version>
    </parent>

    <!-- Additional lines to be added here... -->

    <!-- (you don't need this if you are using a .RELEASE version) -->
    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
            <snapshots><enabled>true</enabled></snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <url>http://repo.spring.io/snapshot</url>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </pluginRepository>
    </pluginRepositories>
</project>

The spring-boot-starter-parent is a special starter that provides useful Maven defaults

spring-boot-starter-parent 提供了一些有用的maven默认配置。

2. 添加依赖

   在pom.xml 文件中的 </parent>下添加

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

   然后运行 mvn dependency:tree命令。

   The mvn dependency:tree command prints a tree representation of your project dependencies

   mvn dependency:tree会打印出项目中的依赖关系

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3. 编码

src/main/java/Example.java

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;

_@RestController_
_@EnableAutoConfiguration_
public class Example {

    _@RequestMapping("/")_
    String home() {
        return "Hello World!";
    }

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

}

@EnableAutoConfiguration. This annotation tells Spring Boot to “guess” how you will want to configure Spring, based on the jar dependencies that you have added. Since spring-boot-starter-web added Tomcat and Spring MVC, the auto-configuration will assume that you are developing a web application and setup Spring accordingly.

@EnableAutoConfiguration这个注解会告诉Spring Boot去'猜‘你想怎样去配置Spring,依靠于你添加的jar依赖。因为spring-boot-starter-web添加了Tomcat和SpringMVC,所以自动配置会假设你正在部署一个web服务器，并且会相应地安装Spring.

4. 运行
   mvn spring-boot:run

访问 http://localhost:8080 会显示 Hello World!

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创建可执行jar

we need to add the spring-boot-maven-plugin to our pom.xml.

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

运行 mvn package