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spring-boot之starter

嚯霍嚯 2022-07-13 阅读 55
springjsonjar包编程语言


文章目录

  • ​​1.如何理解starter​​
  • ​​1.1.模块管理，自动加载Bean到IOC​​
  • ​​1.2.通过spring-boot-starter-web去理解starter概念​​
  • ​​2.自动装载[案例]​​
  • ​​2.1.创建简单的maven项目：demo-spring-boot-starter-example-01​​
  • ​​2.1.1.定义接口类FormatProcessor以及接口方法format()​​
  • ​​2.1.2.定义实现类类StringFormatProcessor以及实现接口方法format()​​
  • ​​2.1.3.定义实现类类JsonFormatProcessor以及实现接口方法format()​​
  • ​​2.1.3.1.引入阿里巴巴的fastjson的jar包​​
  • ​​2.1.3.4.接口实现与方法​​
  • ​​2.1.4.打出jar包​​
  • ​​2.2.在demo-spring-boot-example-06项目中进行引用上面的jar包测试​​
  • ​​2.2.1.创建一个springboot的web项目 demo-spring-boot-example-06​​
  • ​​2.2.2.引入demo-spring-boot-starter-example-01-1.0-SNAPSHOT.jar测试​​
  • ​​2.2.3.创建FormatController进行测试​​
  • ​​2.2.4.启动springboot项目，页面请求验证​​
  • ​​2.2.4.1.启动​​
  • ​​2.2.4.1.页面验证​​
  • ​​2.2.5.总结：无法自动装载bean​​
  • ​​2.2.5.1.FormatController中转载说明​​
  • ​​2.2.5.2.我们的希望:自动注入，如下方式​​
  • ​​2.3.实现demo-spring-boot-starter-example-01的jar中类的自动注入​​

1.如何理解starter

1.1.模块管理，自动加载Bean到IOC

1.Starter 是 Spring Boot 中的一个非常重要的概念，Starter相当于模块，
 它能将模块所需的依赖整合起来并对模块内的Bean根据环境（条件）进行自动配置。
 使用者只需要依赖相应功能的 Starter，无需做过多的配置和依赖，SpringBoot 就能自动扫描并加载相应的模块。

通俗理解

1.比如我们进行spring的web项目开发，这个时候，可能我们没办法知道需要加载那些jar或者没法十分清楚需要的jar包
  这个时候spring-bootstarter-web这个starter就给我们一键式的整理了所有的需要jar
  这样能够更快捷的简化开发，提升开发进度，避免不必要的开发调试jar包依赖的工作，将需要的Bean自动加载到IOC容器之中

1.2.通过spring-boot-starter-web去理解starter概念

从右边我们可以看出来，spring-boot-starter-web 本质上就是将web开发需要的所有的jar包依赖给导入进来了

spring-boot之starter_spring

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starters</artifactId>
    <version>2.2.6.RELEASE</version>
  </parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
  <version>2.2.6.RELEASE</version>
  <name>Spring Boot Web Starter</name>
  <description>Starter for building web, including RESTful, applications using Spring
    MVC. Uses Tomcat as the default embedded container</description>
  <url>https://projects.spring.io/spring-boot/#/spring-boot-parent/spring-boot-starters/spring-boot-starter-web</url>
  <organization>
    <name>Pivotal Software, Inc.</name>
    <url>https://spring.io</url>
  </organization>
  <licenses>
    <license>
      <name>Apache License, Version 2.0</name>
      <url>https://www.apache.org/licenses/LICENSE-2.0</url>
    </license>
  </licenses>
  <developers>
    <developer>
      <name>Pivotal</name>
      <email>info@pivotal.io</email>
      <organization>Pivotal Software, Inc.</organization>
      <organizationUrl>https://www.spring.io</organizationUrl>
    </developer>
  </developers>
  <scm>
    <connection>scm:git:git://github.com/spring-projects/spring-boot.git</connection>
    <developerConnection>scm:git:ssh://git@github.com/spring-projects/spring-boot.git</developerConnection>
    <url>https://github.com/spring-projects/spring-boot</url>
  </scm>
  <issueManagement>
    <system>Github</system>
    <url>https://github.com/spring-projects/spring-boot/issues</url>
  </issueManagement>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
      <version>2.2.6.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-json</artifactId>
      <version>2.2.6.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
      <version>2.2.6.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-validation</artifactId>
      <version>2.2.6.RELEASE</version>
      <scope>compile</scope>
      <exclusions>
        <exclusion>
          <artifactId>tomcat-embed-el</artifactId>
          <groupId>org.apache.tomcat.embed</groupId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>5.2.5.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.2.5.RELEASE</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>
</project>

2.自动装载[案例]

2.1.创建简单的maven项目：demo-spring-boot-starter-example-01

spring-boot之starter_spring_02

spring-boot之starter_spring_03


spring-boot之starter_jar包_04


spring-boot之starter_jar包_05

2.1.1.定义接口类FormatProcessor以及接口方法format()

package com.gaoxinfu.demo.spring.boot.format;

/**
 * @Description:
 * @Author: gaoxinfu
 * @Date: 2020-04-22 08:23
 */
public interface FormatProcessor {

  //主要是一个格式化
  <T> String format(T obj);

}

2.1.2.定义实现类类StringFormatProcessor以及实现接口方法format()

这个字符串的一个传统格式化

package com.gaoxinfu.demo.spring.boot.format;

import java.util.Objects;

/**
 * @Description:
 * @Author: gaoxinfu
 * @Date: 2020-04-22 08:25
 */
public class StringFormatProcessor implements FormatProcessor{
    @Override
    public <T> String format(T obj) {
        return "StringFormatProcessor ="+ Objects.toString(obj) ;
    }
}

2.1.3.定义实现类类JsonFormatProcessor以及实现接口方法format()

主要是用了阿里巴巴的fastjson的json格式化的方法

2.1.3.1.引入阿里巴巴的fastjson的jar包

<dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.61</version>
      <optional>true</optional> -- 意味着引用该jar包可以对包的版本进行选择，不加版本默认1.2.61
    </dependency>

2.1.3.4.接口实现与方法

package com.gaoxinfu.demo.spring.boot.format;

import com.alibaba.fastjson.JSONObject;

/**
 * @Description:
 * @Author: gaoxinfu
 * @Date: 2020-04-22 08:25
 */
public class JsonFormatProcessor implements FormatProcessor{

    @Override
    public <T> String format(T obj) {
        return "JsonFormatProcessor ="+JSONObject.toJSONString(obj);
    }
}

2.1.4.打出jar包

1.  我们这里是要打出一个可以让别的项目可以直接引用使用的jar包
    这里注意下，我们的pom中的package类型为jar，

spring-boot之starter_jar包_06

spring-boot之starter_jar包_07

spring-boot之starter_json_08

2.2.在demo-spring-boot-example-06项目中进行引用上面的jar包测试

2.2.1.创建一个springboot的web项目 demo-spring-boot-example-06

示例截图，创建项springboot的其他步骤不在详细赘述

spring-boot之starter_jar包_09


spring-boot之starter_spring_10

2.2.2.引入demo-spring-boot-starter-example-01-1.0-SNAPSHOT.jar测试

spring-boot之starter_json_11

2.2.3.创建FormatController进行测试

package com.gaoxinfu.demo.spring.boot.controller;

import com.gaoxinfu.demo.spring.boot.format.HelloFormatTemplate;
import com.gaoxinfu.demo.spring.boot.format.StringFormatProcessor;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Description:
 * @Author: gaoxinfu
 * @Date: 2020-04-23 07:38
 */
@RestController
public class FormatController {

    @GetMapping("/oldInvokeWay")
    public String oldInvokeWay(){
        HelloFormatTemplate helloFormatTemplate=new HelloFormatTemplate(new StringFormatProcessor());
        return helloFormatTemplate.doFormat(helloFormatTemplate);
    }
}

2.2.4.启动springboot项目，页面请求验证

2.2.4.1.启动

spring-boot之starter_json_12

spring-boot之starter_spring_13

2.2.4.1.页面验证

spring-boot之starter_jar包_14

2.2.5.总结：无法自动装载bean

2.2.5.1.FormatController中转载说明

可以发现，我们的对象的创建是new出来，并不是引用starter这个项目之后，自动将Bean加载到IOC容器中的，所以我们希望怎么样呢？

spring-boot之starter_jar包_15

2.2.5.2.我们的希望:自动注入，如下方式

spring-boot之starter_spring_16

但是我们在启动的过程中，会发现实际上spring的IOC容器中并没有这个Bean，所以是无法注入的
那么我们如何做到引入jar之后，自动注入呢？

.   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.6.RELEASE)

2020-04-23 08:25:00.918  INFO 9652 --- [           main] d.s.b.DemoSpringBootExample06Application : Starting DemoSpringBootExample06Application on localhost with PID 9652 (/Users/gaoxinfu/demo-spring-boot/demo-spring-boot-example-06/target/classes started by gaoxinfu in /Users/gaoxinfu/demo-spring-boot)
2020-04-23 08:25:00.925  INFO 9652 --- [           main] d.s.b.DemoSpringBootExample06Application : No active profile set, falling back to default profiles: default
2020-04-23 08:25:02.291  INFO 9652 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-04-23 08:25:02.301  INFO 9652 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-04-23 08:25:02.301  INFO 9652 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.33]
2020-04-23 08:25:02.364  INFO 9652 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-04-23 08:25:02.365  INFO 9652 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1299 ms
2020-04-23 08:25:02.426  WARN 9652 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'formatController': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.gaoxinfu.demo.spring.boot.format.HelloFormatTemplate' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@javax.annotation.Resource(shareable=true, lookup=, name=, description=, authenticationType=CONTAINER, type=class java.lang.Object, mappedName=)}
2020-04-23 08:25:02.429  INFO 9652 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2020-04-23 08:25:02.442  INFO 9652 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-04-23 08:25:02.574 ERROR 9652 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

A component required a bean of type 'com.gaoxinfu.demo.spring.boot.format.HelloFormatTemplate' that could not be found.


Action:

Consider defining a bean of type 'com.gaoxinfu.demo.spring.boot.format.HelloFormatTemplate' in your configuration.

Disconnected from the target VM, address: '127.0.0.1:60209', transport: 'socket'

Process finished with exit code 1

2.3.实现demo-spring-boot-starter-example-01的jar中类的自动注入


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