开启Spring Boot

Spring Boot是在Spring框架上创建的一个全新的框架,其设计目的是简化Spring应用的搭建和开发过程。开启Spring Boot有许多种方法可供选择,这里仅介绍使用http://start.spring.io/来构建一个简单的Spring Boot项目。

生成项目文件

访问http://start.spring.io/,页面显示如下:

mrbird_photo_20171129094017.png

这里选择以Maven构建,语言选择Java,Spring Boot版本为1.5.9。然后点击Switch to the full version,可看到更多的配置以及依赖选择:

mrbird_photo_20171129094312.png

在项目信息里选择以jar包的方式部署,Java版本为7。在页面的下方还可以选择诸多的依赖,这里仅选择web进行演示:

mrbird_photo_20171129094913.png

最后点击页面的generate project按钮生成项目文件。文件下载后是一个压缩包,进行解压然后使用eclipse以Maven项目的形式导入。导入后eclipse会自动编译项目并下载相应的依赖,项目目录如下所示:

mrbirdphoto20171129100037.png

简单演示

项目根目录下生成了一个artifactId+Application命名规则的入口类,为了演示简单,不再新建控制器,直接在入口类中编写代码:

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package com.springboot.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@SpringBootApplication
public class DemoApplication {

@RequestMapping("/")
String index() {
return "hello spring boot";
}

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

然后右键点击DemoAppliction,选择run as → Java Application:

mrbirdphoto20171129101138.png

访问http://localhost:8080,页面显示如下:

mrbirdphoto20171129101417.png

打包发布

在eclipse中右击项目,选择run as → Maven build…,如下图所示:

mrbird20171129145655.png

在Goals中输入clean package命令,然后点击下方的run就将项目打包成jar包(初次打包会自动下载一些依赖)。打包完毕后可看到项目目录target文件夹下生成了一个jar文件:

mrbird20171129150126.png

生成jar包后,cd到target目录下,执行以下命令:

mrbird20171129151008.png

访问http://localhost:8080,效果如上。

聊聊pom.xml

打开pom.xml可看到配置如下:

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<?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.springboot</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>demo</name>
<description>Demo project for Spring Boot</description>

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.7</java.version>
</properties>

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

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

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

</project>

spring-boot-starter-parent

spring-boot-starter-parent指定了当前项目为一个Spring Boot项目,它提供了诸多的默认Maven依赖,具体可查看目录D:\m2\repository\org\springframework\boot\spring-boot-dependencies\1.5.9.RELEASE下的spring-boot-dependencies-1.5.9.RELEASE.pom文件,这里仅截取一小部分:

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<properties>
...
<spring-security.version>4.2.3.RELEASE</spring-security.version>
<spring-security-jwt.version>1.0.8.RELEASE</spring-security-jwt.version>
<spring-security-oauth.version>2.0.14.RELEASE</spring-security-oauth.version>
<spring-session.version>1.3.1.RELEASE</spring-session.version>
<spring-social.version>1.1.4.RELEASE</spring-social.version>
<spring-social-facebook.version>2.0.3.RELEASE</spring-social-facebook.version>
<spring-social-linkedin.version>1.0.2.RELEASE</spring-social-linkedin.version>
<spring-social-twitter.version>1.1.2.RELEASE</spring-social-twitter.version>
<spring-ws.version>2.4.2.RELEASE</spring-ws.version>
<sqlite-jdbc.version>3.15.1</sqlite-jdbc.version>
<statsd-client.version>3.1.0</statsd-client.version>
<sun-mail.version>${javax-mail.version}</sun-mail.version>
<thymeleaf.version>2.1.6.RELEASE</thymeleaf.version>
<thymeleaf-extras-springsecurity4.version>2.1.3.RELEASE</thymeleaf-extras-springsecurity4.version>
<thymeleaf-extras-conditionalcomments.version>2.1.2.RELEASE</thymeleaf-extras-conditionalcomments.version>
<thymeleaf-layout-dialect.version>1.4.0</thymeleaf-layout-dialect.version>
<thymeleaf-extras-data-attribute.version>1.3</thymeleaf-extras-data-attribute.version>
<thymeleaf-extras-java8time.version>2.1.0.RELEASE</thymeleaf-extras-java8time.version>
<tomcat.version>8.5.23</tomcat.version>
...
</properties>

需要说明的是,并非所有在<properties>标签中配置了版本号的依赖都有被启用,其启用与否取决于您是否配置了相应的starter。比如tomcat这个依赖就是spring-boot-starter-web的传递性依赖(下面将会描述到)。

当然,我们可以手动改变这些依赖的版本。比如我想把thymeleaf的版本改为3.0.0.RELEASE,我们可以在pom.xml中进行如下配置:

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<properties>
<thymeleaf.version>3.0.0.RELEASE</thymeleaf.version>
</properties>

spring-boot-starter-web

Spring Boot提供了许多开箱即用的依赖模块,这些模块都是以spring-boot-starter-XX命名的。比如要开启Spring Boot的web功能,只需要在pom.xml中配置spring-boot-starter-web即可:

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

因为其依赖于spring-boot-starter-parent,所以这里可以不用配置version。保存后Maven会自动帮我们下载spring-boot-starter-web模块所包含的jar文件。如果需要具体查看spring-boot-starter-web包含了哪些依赖,我们可以右键项目选择run as → Maven Build…,在Goals中输入命令dependency:tree,然后点击run即可在eclipse控制台查看到如下信息:

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[INFO] +- org.springframework.boot:spring-boot-starter-web:jar:1.5.9.RELEASE:compile
[INFO] | +- org.springframework.boot:spring-boot-starter:jar:1.5.9.RELEASE:compile
[INFO] | | +- org.springframework.boot:spring-boot:jar:1.5.9.RELEASE:compile
[INFO] | | +- org.springframework.boot:spring-boot-autoconfigure:jar:1.5.9.RELEASE:compile
[INFO] | | +- org.springframework.boot:spring-boot-starter-logging:jar:1.5.9.RELEASE:compile
[INFO] | | | +- ch.qos.logback:logback-classic:jar:1.1.11:compile
[INFO] | | | | \- ch.qos.logback:logback-core:jar:1.1.11:compile
[INFO] | | | +- org.slf4j:jcl-over-slf4j:jar:1.7.25:compile
[INFO] | | | +- org.slf4j:jul-to-slf4j:jar:1.7.25:compile
[INFO] | | | \- org.slf4j:log4j-over-slf4j:jar:1.7.25:compile
[INFO] | | \- org.yaml:snakeyaml:jar:1.17:runtime
[INFO] | +- org.springframework.boot:spring-boot-starter-tomcat:jar:1.5.9.RELEASE:compile
[INFO] | | +- org.apache.tomcat.embed:tomcat-embed-core:jar:8.5.23:compile
[INFO] | | | \- org.apache.tomcat:tomcat-annotations-api:jar:8.5.23:compile
[INFO] | | +- org.apache.tomcat.embed:tomcat-embed-el:jar:8.5.23:compile
[INFO] | | \- org.apache.tomcat.embed:tomcat-embed-websocket:jar:8.5.23:compile
[INFO] | +- org.hibernate:hibernate-validator:jar:5.3.6.Final:compile
[INFO] | | +- javax.validation:validation-api:jar:1.1.0.Final:compile
[INFO] | | +- org.jboss.logging:jboss-logging:jar:3.3.1.Final:compile
[INFO] | | \- com.fasterxml:classmate:jar:1.3.4:compile
[INFO] | +- com.fasterxml.jackson.core:jackson-databind:jar:2.8.10:compile
[INFO] | | +- com.fasterxml.jackson.core:jackson-annotations:jar:2.8.0:compile
[INFO] | | \- com.fasterxml.jackson.core:jackson-core:jar:2.8.10:compile
[INFO] | +- org.springframework:spring-web:jar:4.3.13.RELEASE:compile
[INFO] | | +- org.springframework:spring-aop:jar:4.3.13.RELEASE:compile
[INFO] | | +- org.springframework:spring-beans:jar:4.3.13.RELEASE:compile
[INFO] | | \- org.springframework:spring-context:jar:4.3.13.RELEASE:compile
[INFO] | \- org.springframework:spring-webmvc:jar:4.3.13.RELEASE:compile
[INFO] | \- org.springframework:spring-expression:jar:4.3.13.RELEASE:compile

上述这些依赖都是隐式依赖于spring-boot-starter-web,我们也可以手动排除一些我们不需要的依赖。

比如spring-boot-starter-web默认集成了tomcat,假如我们想把它换为jetty,可以在pom.xml中spring-boot-starter-web下排除tomcat依赖,然后手动引入jetty依赖:

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

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

tips:依赖的坐标可以到上述的spring-boot-dependencies-1.5.9.RELEASE.pom文件里查找。再次运行dependency:tree

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[INFO] +- org.springframework.boot:spring-boot-starter-web:jar:1.5.9.RELEASE:compile
...
[INFO] +- org.springframework.boot:spring-boot-starter-jetty:jar:1.5.9.RELEASE:compile
[INFO] | +- org.eclipse.jetty:jetty-servlets:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty:jetty-continuation:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty:jetty-http:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty:jetty-util:jar:9.4.7.v20170914:compile
[INFO] | | \- org.eclipse.jetty:jetty-io:jar:9.4.7.v20170914:compile
[INFO] | +- org.eclipse.jetty:jetty-webapp:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty:jetty-xml:jar:9.4.7.v20170914:compile
[INFO] | | \- org.eclipse.jetty:jetty-servlet:jar:9.4.7.v20170914:compile
[INFO] | | \- org.eclipse.jetty:jetty-security:jar:9.4.7.v20170914:compile
[INFO] | | \- org.eclipse.jetty:jetty-server:jar:9.4.7.v20170914:compile
[INFO] | +- org.eclipse.jetty.websocket:websocket-server:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty.websocket:websocket-common:jar:9.4.7.v20170914:compile
[INFO] | | | \- org.eclipse.jetty.websocket:websocket-api:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty.websocket:websocket-client:jar:9.4.7.v20170914:compile
[INFO] | | | \- org.eclipse.jetty:jetty-client:jar:9.4.7.v20170914:compile
[INFO] | | \- org.eclipse.jetty.websocket:websocket-servlet:jar:9.4.7.v20170914:compile
[INFO] | | \- javax.servlet:javax.servlet-api:jar:3.1.0:compile
[INFO] | +- org.eclipse.jetty.websocket:javax-websocket-server-impl:jar:9.4.7.v20170914:compile
[INFO] | | +- org.eclipse.jetty:jetty-annotations:jar:9.4.7.v20170914:compile
[INFO] | | | +- org.eclipse.jetty:jetty-plus:jar:9.4.7.v20170914:compile
[INFO] | | | +- javax.annotation:javax.annotation-api:jar:1.2:compile
[INFO] | | | +- org.ow2.asm:asm:jar:5.1:compile
[INFO] | | | \- org.ow2.asm:asm-commons:jar:5.1:compile
[INFO] | | | \- org.ow2.asm:asm-tree:jar:5.1:compile
[INFO] | | +- org.eclipse.jetty.websocket:javax-websocket-client-impl:jar:9.4.7.v20170914:compile
[INFO] | | \- javax.websocket:javax.websocket-api:jar:1.0:compile
[INFO] | \- org.mortbay.jasper:apache-el:jar:8.0.33:compile

可看到tomcat已被替换为了jetty。

spring-boot-maven-plugin

spring-boot-maven-plugin为Spring Boot Maven插件,提供了:

  1. 把项目打包成一个可执行的超级JAR(uber-JAR),包括把应用程序的所有依赖打入JAR文件内,并为JAR添加一个描述文件,其中的内容能让你用java -jar来运行应用程序。

  2. 搜索public static void main()方法来标记为可运行类。


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