SpringBoot概念介绍和设计理念

作者: 右耳菌 | 来源:发表于2022-07-19 17:08 被阅读0次

SpringBoot介绍

Spring Boot对Spring平台和第三方库进行了整合，可创建可以运行的、独立的、生产级的基于Spring的应用程序。(大多数Spring Boot应用程序只需要很少的Spring配置)
Spring Boot可以使用java -jar或更传统的war部署启动的Java应用程序进行创建，可以内嵌Tomcat 、Jetty .Undertow容器，快速启动web程序。

设计目标

为所有Spring开发提供更快且可通用的入门体验
开箱即用，可以根据需求快速调整默认值。
提供大型项目（例如嵌入式服务器、运行状况检查和统一配置）通用的一系列非功能性功能
绝对没有代码生成，也不需要XML配置。

SpringBoot 优势对比预览

SpringBoot 优势快速预览

1. SpringMVC方式

(1) 修改pom.xml成类似以下的内容

<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>com.study</groupId>
  <artifactId>spring-mvc</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>spring-mvc Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>5.1.5.RELEASE</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
        <scope>provided</scope>
    </dependency>
    
  </dependencies>
  <build>
    <finalName>spring-mvc</finalName>
  </build>
</project>

(2) 创建并修改web.xml成类似以下的内容

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
    
    <!-- 编码过滤 -->
    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
            <param-name>forceEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    
    <!-- springMVC DispatcherServlet 配置 -->
    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <!-- 指定配置文件 -->
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/dispatcher-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet> 
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

(3) 创建并修改dispatcher-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/mvc 
        http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">
    
    <!-- 配置静态资源由web服务器的默认servlet处理 -->
    <mvc:default-servlet-handler />
    
    <!-- 启动注解支持 -->
    <mvc:annotation-driven/> 
    <!--
      <mvc:annotation-driven>  
           <mvc:message-converters register-defaults="true">  -->
               <!-- 避免IE执行AJAX时,返回JSON出现下载文件 -->  
              <!-- <bean id="fastJsonHttpMessageConverter" class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">  
                   <property name="supportedMediaTypes">  
                       <list>  
                           <value>application/json;charset=UTF-8</value>  
                       </list>  
                   </property>  
               </bean>  
           </mvc:message-converters>  
       </mvc:annotation-driven>         
    <mvc:default-servlet-handler/>
    -->
    
    <!-- 配置扫描注解组件的基础包 -->
    <context:component-scan base-package="com.**"/>
    
    
    <!-- 配置视图解析器 -->
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
    </bean>
    
    <!-- 国际化配置 -->   
    <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
        <property name="basename" value="messages"/>
        <!-- <property name="basenames">
            <array>
                <value></value>
            </array>
        </property> -->
    </bean>
     
    <!-- 异常映射配置 -->
    <bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <property name="defaultErrorView" value="/error/error"/>
        <property name="defaultStatusCode" value="500"/>
        <property name="exceptionMappings">
            <props>
                <prop key="java.sql.SQLException">/error/500</prop>
            </props>
        </property>
        <property name="warnLogCategory" value="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"/>
    </bean>
        
</beans>

(4) 创建Controller

package cn.lazyfennec.mvc.controller;

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

@RestController
public class MyController {

    @GetMapping("/index")
    public String index() {
        return "hello world";
    }
}

(5) 部署项目到tomcat

(6) 访问指定地址进行测试

2. SpringBoot方式

(1) 查看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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.8.BUILD-SNAPSHOT</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>cn.lazyfennec</groupId>
    <artifactId>springBootDemo</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <name>springBootDemo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
...  省略部分内容

(2) 创建controller

这里可以类似上方的mvc模式

(3) 运行并且进行测试

可以看到上方的两种方式的比较，SpringBoot的方式比较简单，非常快速，避免了很多的配置，并且无需配置tomcat相关的内容。

Maven工程使用SpringBoot

(1) pom.xml中加入以下内容

dependencyManagement

    <dependencyManagement>
        <dependencies>
            <dependency>
                <!--从SpringBoot导入依赖关系管理-->
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.1.3.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

dependencies

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

(2) 创建启动类

package cn.lazyfennec;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication//由本注解指定启动类
public class SpringBootDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootDemoApplication.class, args);
    }
}

(3) 创建Controller

package cn.lazyfennec.controller;

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

@RestController
public class MyController {

    @GetMapping("/index")
    public String index() {
        return "hello world";
    }
}

运行及打包

1.通过IDEA运行main方法

maven插件运行: mvn spring-boot:run，需要添加spring-boot-maven-plugin到我们的pom.xml文件中

3.创建可执行的jar，需要添加spring-boot-maven-plugin到我们的pom.xml文件中

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

打包命令: mvn package

执行命令: java -jar xxx.jar

注意事项: jar文件生成在target目录下，**..jar.original这个文件一般很小，这是打包可执行jar文件之前的原始jar

一些需要注意的东西

程序入口: Main方法

@SpringBootApplication//由本注解指定启动类
public class SpringBootDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootDemoApplication.class, args);
    }
}

SpringBoot中通用的约定

注解扫码的包目录basePackage为启动类Main函数入口所在的包路
配置文件约定是classpath目录下的application.yml或者application.properties
web开发的静态文件放在classpath，访问的顺序依次是:
/META-INF/resources -> resources -> static -> public
web开发中页面模板，约定放在classpath目录，/templates/目录下

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