Dependency Injection
In this case, in an action or event, for example, you want to write now, then you need a pen, so you have a new pen to write, here, you use the new pen, you this action and the pen has a connection, without a pen, you can not write the word, that is, your behavior depends on the pen, They make up the dependency relationship. Or if you want to assemble a computer (Transaction) Now, you need objects such as monitors, motherboards, and key-mouse optical drives, which are usually new, and that the new object and the current (this) object have dependencies.
Spring is injected with dependent objects, which is often called dependency injection.
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About the jar package in spring
1:core Core package, AOP oriented aspect, BEAN:IOC Foundation implementation, Context Extension and Enterprise Services, context-support to context enhancement; JDBC database; TX transaction; Test testing; ORM integrates third-party persistence layer; OXM mapping/ Toggle support; Aspects integrated aspectj;expression expression Language; Instrument proxy tool; Instrument-tomcat:tomcat class loader extension;
2:jms/messaging did not study, do not know the difference, the message service, Web:web development and other framework integration, WEBMVC:VC part, like STRUTS/JSF, webmvc portlet:webmvc enhancement; WebSocket: WebSocket communication, look at the source code or anti-compilation through the package name to know the package function, the individual package only one or two classes, specific application in accordance with the requirements of the Guide package, Basic Package core/aop/bean/context/jdbc/tx/orm/oxm/
3:aspects/web, in fact, Spring provides a lot of auxiliary tools, we all like to re-encapsulate the framework, such as Hibernate/extjs, in fact, there is absolutely no need.
"Java EE Spring" 15, some concepts in spring