白话Spring源码（三）：spring框架的理解

待我称王封你为后i 2022-04-06 05:41 269阅读 0赞

### 一、为什么需要Spring ###

我们想一下如果没有spring框架我们是怎么去开发web应用呢？

我估计大部分代码是跟业务无关而跟底层或者网络接口交互；对象，模块关系错综复杂；开发周期特别的长很容易流产；后期维护时代码会越来越烂，最后可能无法维护。。。

那spring框架给我们解决什么问题了呢？

1.封装非业务的代码，我们只需开发业务功能：比如获取请求的数据，保存数据库，事务等等

2.统一创建对象，维护对象的关系和生命周期

3.方便的对方法加入通用的代码

4.简化与其他框架的结合使用

总的来说就是为了简化我们企业应用开发的难度，让我们只关注业务功能的开发！

据说开发spring框架是大神也是一位音乐家，所以我们会发现他写的代码很有艺术感，哈哈哈。。。

### 二、Spring框架的定义 ###

Spring is a layered Java/J2EE application framework, based on code published in "Expert One-on-One J2EE Design
    and Development" by Rod Johnson (Wrox, 2002). Spring includes:
    
    * Powerful JavaBeans-based configuration management, applying Inversion-of-Control principles. This makes
    wiring up applications quick and easy. No more singletons littered throughout your codebase, no more arbitrary
    properties files: one consistent and elegant approach everywhere. This core bean factory can be used in any
    environment, from applets to J2EE containers.
    
    * Generic abstraction layer for transaction management, allowing for pluggable transaction managers, and making
    it easy to demarcate transactions without dealing with low-level issues. Generic strategies for JTA and a
    single JDBC DataSource are included. In contrast to plain JTA or EJB CMT, Spring's transaction support is not
    tied to J2EE environments.
    
    * JDBC abstraction layer that offers a meaningful exception hierarchy (no more pulling vendor codes out of
    SQLException), simplifies error handling, and greatly reduces the amount of code you'll need to write.
    You'll never need to write another finally block to use JDBC again. The JDBC-oriented exceptions comply to
    Spring's generic DAO exception hierarchy.
    
    * Integration with Hibernate, JDO, and iBATIS SQL Maps: in terms of resource holders, DAO implementation
    support, and transaction strategies. First-class Hibernate support with lots of IoC convenience features,
    addressing many typical Hibernate integration issues. All of these comply to Spring's generic transaction
    and DAO exception hierarchies.
    
    * AOP functionality, fully integrated into Spring configuration management. You can AOP-enable any object managed
    by Spring, adding aspects such as declarative transaction management. With Spring, you can have declarative
    transaction management without EJB... even without JTA, if you're using a single database in Tomcat or another
    web container without JTA support.
    
    * Flexible MVC web application framework, built on core Spring functionality. This framework is highly configurable
    via strategy interfaces, and accommodates multiple view technologies like JSP, Tiles, Velocity, FreeMarker, iText,
    and POI. Note that a Spring middle tier can easily be combined with a web tier based on any other web MVC framework,
    like Struts, WebWork, or Tapestry.
    
    You can use all of Spring's functionality in any J2EE server, and most of it also in non-managed environments.
    A central focus of Spring is to allow for reusable business and data access objects that are not tied to specific
    J2EE services. Such objects can be reused across J2EE environments (web or EJB), standalone applications, test
    environments, etc without any hassle.
    
    Spring has a layered architecture; all its functionality builds on lower levels. So you can e.g. use the
    JavaBeans configuration management without using the MVC framework or AOP support. But if you use the web MVC
    framework or AOP support, you'll find they build on the configuration framework, so you can apply your knowledge
    about it immediately.

上面是spring的开发者Rod Johnson对spring的介绍，为什么我贴出英文的呢？因为很多翻译过来的就变味了，我们程序员还是要坚持看英文原版的一些概念的解释，这样会更好的去理解作者的本意。

### 三、spring架构 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hhb3hpbjk2Mw_size_16_color_FFFFFF_t_70][]

从这张官方的架构图种我们可以看出，spring Core是其他模块的基础，也是spring的核心模块，各模块的作用如下：

* "spring-core" (~185 KB)
    - Contents: bean container, core utilities
    - Dependencies: Commons Logging, (Log4J)
    
    * "spring-aop" (~110 KB)
    - Contents: AOP framework, source-level metadata support
    - Dependencies: spring-core, AOP Alliance, (CGLIB, Commons Attributes)
    
    * "spring-context" (~160 KB)
    - Contents: application context, validation framework, UI support, JNDI, mail, EJB, remoting, scheduling
    - Dependencies: spring-core, (Velocity, FreeMarker, JavaMail, EJB, JAX-RPC, Hessian, Burlap, Quartz)
    
    * "spring-dao" (~175 KB)
    - Contents: DAO support, transaction infrastructure, JDBC support
    - Dependencies: spring-core, (spring-aop, JTA)
    
    * "spring-orm" (~110 KB)
    - Contents: Hibernate support, JDO support, iBATIS SQL Maps support
    - Dependencies: spring-dao, (Hibernate, JDO, iBATIS SQL Maps)
    
    * "spring-web" (~70 KB)
    - Contents: web application context, multipart resolver, web utilities
    - Dependencies: spring-context, Servlet, (Commons FileUpload, COS)
    
    * "spring-webmvc" (~135 KB)
    - Contents: web MVC framework, web controllers, web views
    - Dependencies: spring-web, (JSP, JSTL, Tiles, iText, POI)

### 四、spring1.0源码地址 ###

[https://gitee.com/haoxin963/spring-framework-1.0][https_gitee.com_haoxin963_spring-framework-1.0]

大家可以去下载，开始学习spring源码之旅吧！

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hhb3hpbjk2Mw_size_16_color_FFFFFF_t_70]: /images/20220406/a19715d1866544f39885a89a03e9bd7d.png
[https_gitee.com_haoxin963_spring-framework-1.0]: https://gitee.com/haoxin963/spring-framework-1.0