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Spring 源码分析(二)--容器的基本实现

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标签:contents   exist   conf   打印   spring   print   fresh   exception   err   

    容器最基本的实现是beanFactory,但是大部分企业引用都是使用ApplicationContext,这里介绍基础的BeanFactory是为了更好的理解sping内部原理。

(一)基本用法

(1)bean的声明

package com.ws.learn.entity;

public class Person {
    private String name;
    private Integer age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public void info(){
        System.out.println("name:"+getName()+" age:"+getAge());
    }
}

 

(2)配置文件beanFactoryTest.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.springframework.org/schema/beans" xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <bean id="person" class="com.ws.learn.entity.Person">
        <property name="name" value="test"/>
        <property name="age" value="18"/>
    </bean>
</beans>

(3)测试

public class MyTest {
    public static void main(String[] args){
        BeanFactory bf = new XmlBeanFactory(new ClassPathResource("beanFactoryTest.xml"));//读取beanFactoryTest.xml中的内容
        Person p = bf.getBean("person",Person.class);
        p.info();
    }
}

 

(二)核心类介绍

(1)DefaultListableBeanFactory

    XmlBeanFactory继承自DefaultListableBeanFactory,而DefaultListableBeanFactory是整个bean加载的核心部分,是Spring注册及加载bean的默认实现,而对于XmlBeanFactory与DefaultListableBeanFactory不同的地方其实是在XmlBeanFactory中使用了自定义的XML读取器XmlBeanDefinitionReader,实现了个性化的BeanDefinitionReader读取,DefaultListableBeanFactory继承了AbstractAutowireCapableBeanFactory并实现了ConfigURableListableBeanFactory以及BeanDefinitionRegistry接口。以下是ConfigURationListableBeanFactory的层次结构图以下相关类图

    技术分享图片

容器加载相关类图:

     技术分享图片

类图中各个类的作用:

  • AliasRegistry:定义对alias的简单增删改等操作
  • SimpleAliasRegistry:主要使用map作为alias的缓存,并对接口AliasRegistry进行实现
  • SingletonBeanRegistry:定义对单例的注册及获取
  • BeanFactory:定义获取bean及bean的各种属性
  • DefaultSingletonBeanRegistry:对接口SingletonBeanRegistry各函数的实现
  • HierarchicalBeanFactory:继承BeanFactory,也就是在BeanFactory定义的功能的基础上增加了对parentFactory的支持
  • BeanDefinitionRegistry:定义对BeanDefinition的各种增删改操作
  • FactoryBeanRegistrySupport:在DefaultSingletonBeanRegistry基础上增加了对FactoryBean的特殊处理功能
  • ConfigurableBeanFactory:提供配置Factory的各种方法
  • ListableBeanFactory:根据各种条件获取bean的配置清单
  • AbstractBeanFactory:综合FactoryBeanRegistrySupport和ConfigurationBeanFactory的功能
  • AutowireCapableBeanFactory:提供创建bean、自动注入、初始化以及应用bean的后处理器
  • AbstractAutowireCapableBeanFactory:综合AbstractBeanFactory并对接口AutowireCapableBeanFactory进行实现
  • ConfigurableListableBeanFactory:BeanFactory配置清单,指定忽略类型及接口等
  • DefaultListableBeanFactory:综合上面所有功能,主要是对Bean注册后的处理

 

(2)XmlBeanDefinitionReader

XML配置文件的读取是Spring中重要的功能,因为Spring的大部分功能都是以配置作为切入点的,可以从XmlBeanDefinitionReader中梳理一下资源文件读取、解析及注册的大致脉络,首先看看各个类的功能

  • ResourceLoader:定义资源加载器,主要应用于根据给定的资源文件地址返回对应的Resource
  • BeanDefinitionReader:主要定义资源文件读取并转换为BeanDefinition的各个功能
  • EnvironmentCapable:定义获取Environment方法
  • DocumentLoader:定义从资源文件加载到转换为Document的功能
  • AbstractBeanDefinitionReader:对EnvironmentCapable、BeanDefinitionReader类定义的功能进行实现
  • BeanDefinitionDocumentReader:定义读取Document并注册BeanDefinition功能
  • BeanDefinitionParserDelegate:定义解析Element的各种方法

整个XML配置文件读取的大致流程,在XmlBeanDefinitionReader中主要包含以下几步处理:

技术分享图片 

  (1)通过继承自AbstractBeanDefinitionReader中的方法,来使用ResourceLoader将资源文件路径转换为对应的Resource文件

  (2)通过DocumentLoader对Resource文件进行转换,将Resource文件转换为Document文件

  (3)通过实现接口BeanDefinitionDocumentReader的DefaultBeanDefinitionDocumentReader类对Document进行解析,并使用BeanDefinitionParserDelegate对Element进行解析

 

(三)容器的基础XmlBeanFactory

BeanFactory bf = new XmlBeanFactory(new ClassPathResource("beanFactoryTest.xml"));

通过XmlBeanFactory初始化时序图看一看上面代码的执行逻辑

  技术分享图片

 

    首先调用ClassPathResource的构造函数来构造Resource资源文件的实例对象,这样后续的资源处理就可以用Resource提供的各种服务来操作了。

 

配置文件封装

    Spring的配置文件读取是通过ClassPathResource进行封装的,Spring对其内部使用到的资源实现了自己的抽象结构:Resource接口来封装底层资源

public interface InputStreamSource {

    /**
     * Return an {@link InputStream} for the content of an underlying resource.
     * <p>It is expected that each call creates a <i>fresh</i> stream.
     * <p>This requirement is particularly important when you consider an API such
     * as JavaMail, which needs to be able to read the stream multiple times when
     * creating mail attachments. For such a use case, it is <i>required</i>
     * that each {@code getInputStream()} call returns a fresh stream.
     * @return the input stream for the underlying resource (must not be {@code null})
     * @throws java.io.FileNotFoundException if the underlying resource doesn‘t exist
     * @throws IOException if the content stream could not be opened
     */
    InputStream getInputStream() throws IOException;

}

 

public interface Resource extends InputStreamSource {

    /**
     * Determine whether this resource actually exists in physical form.
     * <p>This method performs a definitive existence check, whereas the
     * existence of a {@code Resource} handle only guarantees a valid
     * descriptor handle.
     */
    boolean exists();

    /**
     * Indicate whether the contents of this resource can be read via
     * {@link #getInputStream()}.
     * <p>Will be {@code true} for typical resource descriptors;
     * note that actual content reading may still fail when attempted.
     * However, a value of {@code false} is a definitive indication
     * that the resource content cannot be read.
     * @see #getInputStream()
     */
    boolean isReadable();

    /**
     * Indicate whether this resource represents a handle with an open stream.
     * If {@code true}, the InputStream cannot be read multiple times,
     * and must be read and closed to avoid resource leaks.
     * <p>Will be {@code false} for typical resource descriptors.
     */
    boolean isOpen();

    /**
     * Return a URL handle for this resource.
     * @throws IOException if the resource cannot be resolved as URL,
     * i.e. if the resource is not available as descriptor
     */
    URL getURL() throws IOException;

    /**
     * Return a URI handle for this resource.
     * @throws IOException if the resource cannot be resolved as URI,
     * i.e. if the resource is not available as descriptor
     * @since 2.5
     */
    URI getURI() throws IOException;

    /**
     * Return a File handle for this resource.
     * @throws java.io.FileNotFoundException if the resource cannot be resolved as
     * absolute file path, i.e. if the resource is not available in a file system
     * @throws IOException in case of general resolution/reading failures
     * @see #getInputStream()
     */
    File getFile() throws IOException;

    /**
     * Determine the content length for this resource.
     * @throws IOException if the resource cannot be resolved
     * (in the file system or as some other known physical resource type)
     */
    long contentLength() throws IOException;

    /**
     * Determine the last-modified timestamp for this resource.
     * @throws IOException if the resource cannot be resolved
     * (in the file system or as some other known physical resource type)
     */
    long lastModified() throws IOException;

    /**
     * Create a resource relative to this resource.
     * @param relativePath the relative path (relative to this resource)
     * @return the resource handle for the relative resource
     * @throws IOException if the relative resource cannot be determined
     */
    Resource createRelative(String relativePath) throws IOException;

    /**
     * Determine a filename for this resource, i.e. typically the last
     * part of the path: for example, "myfile.txt".
     * <p>Returns {@code null} if this type of resource does not
     * have a filename.
     */
    String getFilename();

    /**
     * Return a description for this resource,
     * to be used for error output when working with the resource.
     * <p>Implementations are also encouraged to return this value
     * from their {@code toString} method.
     * @see Object#toString()
     */
    String getDescription();

}

    

    InputStreamSource封装任何能返回InputStream的类,比如File、Classpath下的资源和Byte Array等, 它只有一个方法定义:getInputStream(),该方法返回一个新的InputStream对象

    Resource接口抽象了所有Spring内部使用到的底层资源:File、URL、Classpath等。首先,它定义了3个判断当前资源状态的方法:存在性(exists)、可读性(isReadable)、是否处于打开状态(isOpen)。另外,Resource接口还提供了不同资源到URL、URI、File类型的转换,以及获取lastModified属性、文件名(不带路径信息的文件名,getFilename())的方法,为了便于操作,Resource还提供了基于当前资源创建一个相对资源的方法:createRelative(),还提供了getDescription()方法用于在错误处理中的打印信息

对不同来源的资源文件都有相应的Resource实现:文件(FileSystemResource)、Classpath资源(ClassPathResource)、URL资源(UrlResource)、InputStream资源(InputStreamResource)、Byte数组(ByteArrayResource)等,相关类图如下所示:

                    技术分享图片

 

Spring 源码分析(二)--容器的基本实现

标签:contents   exist   conf   打印   spring   print   fresh   exception   err   

原文地址:https://www.cnblogs.com/fdzfd/p/8371404.html

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