如何手写一个Spring Boot Starter

public class Person {
 private String name;
 private int age;
 private String address;
 public Person(String name, int age, String address) {
  super();
  this.name = name;
  this.age = age;
  this.address = address;
 }
 // 省略get和set方法
}

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.nobody</groupId>
	<artifactId>myjson-spring-boot-starter</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>myjson-spring-boot-starter</name>
	<description>Demo project for Spring Boot Starter</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
			<version>2.3.8.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-configuration-processor</artifactId>
			<version>2.3.8.RELEASE</version>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>fastjson</artifactId>
			<version>1.2.73</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-autoconfigure</artifactId>
			<version>2.3.8.RELEASE</version>
		</dependency>
	</dependencies>
</project>

package com.nobody.myjson.service;

import com.alibaba.fastjson.JSON;

/**
 * @Description 业务处理类
 * @Author Mr.nobody
 * @Date 2021/2/27
 * @Version 1.0
 */
public class MyJsonService {
 // 前缀
 private String prefixName;
 // 后缀
 private String suffixName;

 /**
  * 将Java对象转为带有指定前后缀的JSON字符串
  * 
  * @param o 需要转换的Java对象
  * @return 转换后的字符串
  */
 public String objectToMyJson(Object o) {
  return prefixName + JSON.toJSONString(o) + suffixName;
 }

 public String getPrefixName() {
  return prefixName;
 }

 public void setPrefixName(String prefixName) {
  this.prefixName = prefixName;
 }

 public String getSuffixName() {
  return suffixName;
 }

 public void setSuffixName(String suffixName) {
  this.suffixName = suffixName;
 }
}
配置类，定义需要的配置信息和默认配置项，并指明关联配置文件的配置项前缀。它可以把相同前缀的配置信息通过配置项名称映射成实体类的属性中。

package com.nobody.myjson.config;

import org.springframework.boot.context.properties.ConfigurationProperties;

/**
 * @Description 配置类(类名一般为模块名+Properties) nobody.json为Starter使用者通过yml配置文件动态修改属性值的变量名前缀
 * @Author Mr.nobody
 * @Date 2021/2/27
 * @Version 1.0
 */
@ConfigurationProperties(prefix = "nobody.json")
public class MyJsonProperties {

 // Starter使用者没在配置文件中配置prefixName属性的值时的默认值
 public static final String DEFAULT_PREFIX_NAME = "@";

 // Starter使用者没在配置文件中配置suffixName属性的值时的默认值
 public static final String DEFAULT_SUFFIX_NAME = "@";

 private String prefixName = DEFAULT_PREFIX_NAME;

 private String suffixName = DEFAULT_SUFFIX_NAME;

 public String getPrefixName() {
  return prefixName;
 }

 public void setPrefixName(String prefixName) {
  this.prefixName = prefixName;
 }

 public String getSuffixName() {
  return suffixName;
 }

 public void setSuffixName(String suffixName) {
  this.suffixName = suffixName;
 }
}

package com.nobody.myjson.config;

import com.nobody.myjson.service.MyJsonService;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @Description 自动装配类
 * @Author Mr.nobody
 * @Date 2021/2/27
 * @Version 1.0
 */
@Configuration // 标识此类是配置类
@ConditionalOnClass(MyJsonService.class) // 表示只有指定的class在classpath上时才能被注册
@EnableConfigurationProperties(MyJsonProperties.class) // 激活@ConfigurationProperties
public class MyJsonConfiguration {

 private MyJsonProperties myJsonProperties;

 // 自动注入配置类
 public MyJsonConfiguration(MyJsonProperties myJsonProperties) {
  this.myJsonProperties = myJsonProperties;
 }

 // 创建MyJsonService对象，注入到Spring容器中
 @Bean
 @ConditionalOnMissingBean(MyJsonService.class) // 当容器没有此bean时，才注册
 public MyJsonService myJsonService() {
  MyJsonService myJsonService = new MyJsonService();
  myJsonService.setPrefixName(myJsonProperties.getPrefixName());
  myJsonService.setSuffixName(myJsonProperties.getSuffixName());
  return myJsonService;
 }
}

<dependency>
 <groupId>com.nobody</groupId>
 <artifactId>myjson-spring-boot-starter</artifactId>
 <version>0.0.1-SNAPSHOT</version>
</dependency>

package com.nobody.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.nobody.domain.Person;
import com.nobody.service.MyJsonService;

@RestController
@RequestMapping("demo")
public class DemoController {
 
 // 注入我们Starter中的服务类
 @Autowired
 private MyJsonService myJsonService;
 
 @GetMapping()
 public String test() {
  Person p = new Person("Mr.nobody", 18, "拉斯维加斯");
  // 调用服务方法
  return myJsonService.objectToMyJson(p);
 }
}

nobody: 
 json:
 prefixName: HH
 suffixName: KK

// 创建MyJsonService对象，注入到Spring容器中
@Bean
@ConditionalOnProperty(name = "nobody.json.enable", matchIfMissing = true)
@ConditionalOnMissingBean(MyJsonService.class) // 当容器没有此bean时，才注册
public MyJsonService myJsonService() {
 MyJsonService myJsonService = new MyJsonService();
 myJsonService.setPrefixName(myJsonProperties.getPrefixName());
 myJsonService.setSuffixName(myJsonProperties.getSuffixName());
 return myJsonService;
}