Spring 中 Xml 属性配置的解析过程

心已赠人 2022-11-08 11:26 114阅读 0赞

# 1 工程概述 #

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## 1.1 pom文件 ##

<properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <maven.compiler.source>1.8</maven.compiler.source>
            <maven.compiler.target>1.8</maven.compiler.target>
            <spring.version>5.2.8.RELEASE</spring.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.13</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>${spring.version}</version>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.16.20</version>
            </dependency>
            
            <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
                <version>1.7.10</version>
            </dependency>
            <dependency>
                <groupId>ch.qos.logback</groupId>
                <artifactId>logback-classic</artifactId>
                <version>1.1.2</version>
            </dependency>
            <dependency>
                <groupId>ch.qos.logback</groupId>
                <artifactId>logback-core</artifactId>
                <version>1.1.2</version>
            </dependency>
        </dependencies>

## 1.2 applicationContext.xml ##

## 1.3 StudentBean ##

@Data
    @AllArgsConstructor
    @NoArgsConstructor
    @ToString
    public class StudentBean { 
    
    
        private String name = "rosh";
    
        private String school = "杜桥中学";
    
        private String hobby = "篮球";
    
    }

## 1.4 RoshTest ##

public class RoshTest { 
    
        @Test
        public void mainTest(){ 
            ClassPathXmlApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml");
            StudentBean student = applicationContext.getBean(StudentBean.class);
            System.out.println(student.toString());
    
        }
    }

## 1.5 运行结果 ##

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# 2 流程解析 #

## 2.1 源码Debug ##

**描述**：调用构造方法中的refresh方法  
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**描述**：调用AbstractApplicationContext refresh()方法进行xml解析  
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**重点：** 创建XML对象的解析器  
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**重点：** 用xml文件解析器把xml文件转换成Reource对象  
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**重点：** Resource对象转Document对象  
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\*\*重点：\*\*创建Document解析器  
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**总结：** DefaultBeanDefinitionDocumentReader（Document解析器）解析xml文件  
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## 2.2 总结流程 ##

**大概步骤：**  
(1) 构造。  
(2) 刷新工厂。  
(3) 创建xml对象解析器。  
(4) 将xml解析成Resource对象。  
(5) Resource转Document。  
(6) 创建Document对象解析器。  
(7) 解析Document对象。

**详细步骤：**

1 ClassPathXmlApplicationContext调用构造方法。
    2 AbstractApplicationContext：
       (1) 调用refresh()方法。
       (2) 调用obtainFreshBeanFactory()方法。
    3 AbstractRefreshableApplicationContext调用refreshBeanFactory() 方法。
    4 AbstractXmlApplicationContext：
    	(1) loadBeanDefinitions(DefaultListableBeanFactory beanFactory)方法。创建XML解析器。
        (2) 调用loadBeanDefinitions(XmlBeanDefinitionReader reader)方法。
    5 AbstractBeanDefinitionReader：
    	(1) loadBeanDefinitions(String... locations)方法。     
    	(2) loadBeanDefinitions(String location)方法。
    	(3) loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources)方法，将XML解析成Resource对象。	
    	(4) loadBeanDefinitions(Resource... resources)方法。
    6 XmlBeanDefinitionReader:
    	(1) loadBeanDefinitions(Resource resource) 方法。
    	(2) loadBeanDefinitions(EncodedResource encodedResource) 方法。
    	(3) doLoadBeanDefinitions(InputSource inputSource, Resource resource)方法。
    	(4)	registerBeanDefinitions(Document doc, Resource resource)方法。创建Document解析器。
    7 DefaultBeanDefinitionDocumentReader：
        (1) registerBeanDefinitions(Document doc, XmlReaderContext readerContext)方法。
        (2) doRegisterBeanDefinitions(Element root)方法。
        (3) parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) 方法解析默认标签、自定义标签。

# 3 解析Bean标签 #

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# 4 自定义标签解析 #

## 4.1 步骤 ##

1. 获取自定义标签的 namespace 命令空间，例如：http://www.springframework.org/schema/context
    2. 根据命令空间获取 NamespaceHandler 对象通过 SPI 机制获取 spring 中所有 jar 包里面的 "META-INF/spring.handlers"
    文件，并且建立映射关系
    3. 反射获取 NamespaceHandler 实例
    4. 调用对应标签如 ContextNameHandler 标签的 init()方法
    5. 调用 handler.parse()方法完成解析

## 4.2 流程解析 ##

1 根据自定义标签寻找相应的uri  
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2 加载spring中全部MET-INF/spring.handlers  
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3 根据applicationContext.xml 找对应的Hadnler  
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## 4.3 Debug ##

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