Spring源码分析：List集合注入

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>

    <groupId>org.example</groupId>
    <artifactId>spring-boot-test</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <java.version>11</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <spring-boot.version>2.4.2</spring-boot.version>
        <spring-cloud.version>2020.0.1</spring-cloud.version>
        <spring-cloud-alibaba.version>2021.1</spring-cloud-alibaba.version>

        <knife4j.version>4.1.0</knife4j.version>
        <hutool.version>5.6.1</hutool.version>
        <lombok.version>1.18.22</lombok.version>

        <maven.plugin.version>2.7.8</maven.plugin.version>
    </properties>

    <!-- 依赖声明 -->
    <dependencyManagement>
        <dependencies>
            <!-- SpringCloud 微服务 -->
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <!-- SpringCloud Alibaba 微服务 -->
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>${spring-cloud-alibaba.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <!-- SpringBoot 依赖配置 -->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <!--文档插件-->
            <dependency>
                <groupId>com.github.xiaoymin</groupId>
                <artifactId>knife4j-openapi2-spring-boot-starter</artifactId>
                <version>${knife4j.version}</version>
            </dependency>

            <!-- hutool工具 -->
            <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
                <version>${hutool.version}</version>
            </dependency>

            <!-- lombok -->
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>${lombok.version}</version>
            </dependency>

        </dependencies>
    </dependencyManagement>

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

        <!--SpringBoot Actuator-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <!--请求参数校验-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>

        <!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>${lombok.version}</version>
            <optional>true</optional>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                    <encoding>${project.build.sourceEncoding}</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

EvaluationProcess 接口

package org.example.process;

public interface EvaluationProcess {

    void process(Object object);

    boolean supports(Integer type);

}

ConsultingEvaluationProcess 类

package org.example.process.impl;

import org.example.process.EvaluationProcess;
import org.springframework.stereotype.Service;

@Service
public class ConsultingEvaluationProcess implements EvaluationProcess {

    @Override
    public void process(Object object) {
        System.out.println("ConsultingEvaluationProcess");
    }

    @Override
    public boolean supports(Integer type) {
        return type == 1;
    }
}

DiagnoseEvaluationProcess类

package org.example.process.impl;

import org.example.process.EvaluationProcess;
import org.springframework.stereotype.Service;

@Service
public class DiagnoseEvaluationProcess implements EvaluationProcess {
    @Override
    public void process(Object object) {
        System.out.println("DiagnoseEvaluationProcess");
    }

    @Override
    public boolean supports(Integer type) {
        return type == 2;
    }
}

EvaluationService  业务类

package org.example.process;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class EvaluationService {

    //集合注入
    @Autowired
    private List<EvaluationProcess> evaluationProcesses;

    private Optional<EvaluationProcess> getProcess(Integer type) {
        if (this.evaluationProcesses != null) {
            return this.evaluationProcesses.stream().filter(a -> a.supports(type)).findFirst();
        }
        return Optional.empty();
    }

    public void save() {
        getProcess(1).ifPresent(origin -> origin.process(null));
    }
}

ScanConfig 配置

package org.example.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("org.example.process")
public class ScanConfig {


}

测试类  Test

package org.example.process;

import org.example.config.ScanConfig;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Test {

    public static void main(String[] args) {
        //纯注解
        ApplicationContext c1 = new AnnotationConfigApplicationContext(ScanConfig.class);

        EvaluationService bean = c1.getBean(EvaluationService.class);
        bean.save();
    }
}

源码分析：

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean(java.lang.String, org.springframework.beans.factory.support.RootBeanDefinition, java.lang.Object[])
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#populateBean
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor#postProcessProperties
org.springframework.beans.factory.annotation.InjectionMetadata#inject
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.AutowiredFieldElement#inject
org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver#getLazyResolutionProxyIfNecessary
org.springframework.beans.factory.support.DefaultListableBeanFactory#resolveMultipleBeans