手拆框架之Spring IOC 環境準備篇

開始以前:本文滿滿的圖片。請你們在閱讀以前準備好流量，以防爆表。哈哈。第一次寫IOC的文章，但願你們多多支持，謝謝。

 

本文主要針對ClasspathXmlApplicationContext(還有與之相似的FileSystemXml...)的總體初始化流程作講解。若有疑問能夠加QQ羣: 77174608 來討論。

 

主題開始:

 

讀源碼準備的環境:

 

maven, logback基礎知識, Spring 相關使用經驗。

 

進入正文: 首先開始pom.xml

<properties>
        <spring.version>4.3.14.RELEASE</spring.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-asm -->
        <!-- 注意，這裏是第一個坑，在高版本的spring中是不須要手動引入該依賴了，若是引入則會拋出 java.lang.IncompatibleClassChangeError: class org.springframework.core.type.classreading.ClassMetadataReadingVisitor has interface org.springframework.asm.ClassVisitor as super class 異常 -->
        <!--<dependency>-->
            <!--<groupId>org.springframework</groupId>-->
            <!--<artifactId>spring-asm</artifactId>-->
            <!--<version>3.1.4.RELEASE</version>-->
        <!--</dependency>-->

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>1.7.21</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.7</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aspects</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-expression</artifactId>
            <version>${spring.version}</version>
        </dependency>
    </dependencies>

 

logback配置:

<appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} %contextName [%thread] %-5level %logger{36} - %msg%n
            </pattern>
        </encoder>
    </appender>

    <logger name="org.springframework" additivity="false" level="debug">
        <appender-ref ref="console"/>
    </logger>

 

我這裏使用了自動掃包，因此beans.xml配置爲:

<context:annotation-config/>

<context:component-scan base-package="com.autorun.spring.demo"/>

ok, 環境已經基本已經搞定，咱們開始寫基本類

package com.autorun.spring.demo.beans;

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

/**
 * @author Autorun
 *         Created by Autorun on 2018/3/4.
 */
@Component
public class A {


    @Autowired
    private B b;

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        A a = (A) o;

        return b != null ? b.equals(a.b) : a.b == null;
    }

    @Override
    public int hashCode() {
        return b != null ? b.hashCode() : 0;
    }

    @Override
    public String toString() {
        return "A{" +
                ", b=" + b +
                '}';
    }
}

package com.autorun.spring.demo.beans;

import org.springframework.stereotype.Component;

/**
 * @author Autorun
 * Created by Autorun on 2018/3/4.
 */
@Component
public class B {
}

而後建立主類(固然, 目前spring仍是主要用於web開發,有用過springboot的童鞋應該對這種玩法有所瞭解。再也不贅述):

public class Application {

    public static void main(String[] args) {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans-parent.xml");
        ctx.setDisplayName("parent");
        ///        ctx.start();
        A a = ctx.getBean(A.class);
        System.out.println(a);
        B b = ctx.getBean(B.class);
        System.out.println(b);
    }

​以上就是環境準備篇。畢竟基礎。下一篇將正式開始源碼拆解。 前幾篇文章會粗略的走一遍加載，目的是讓你們熟悉一下總體流程。以後會對每一個組件進行講解。謝謝你們支持