Explain in detail the life cycle, scope and implementation of beans in spring

preface

In ApplicationContext After configuring beans in XML, what are the declaration Cycle States of beans. What can be done at each stage of the life cycle. In ApplicationContext What are the scopes of XML configuration beans. What does each scope represent. For what situation. Make a record of this article.

life cycle

initialization

You can directly view the pictures from the spring bean life cycle

As can be seen from the above figure, bean initialization includes 9 steps. Some of these steps include the implementation of the interface, including beannameaware interface and beanfactoryaware interface. Applicationcontextaware interface. Beanpostprocessor interface, initializingbean interface. So what role do these interfaces play throughout the life cycle? We will introduce them one by one later.

Before instantiation

When all the attributes of a bean are set, it is often necessary to perform some specific behaviors. Spring provides two ways to achieve this function:

Specify initialization method

As follows:

Write loader

Configure bean

Note the init method parameter

results of enforcement

Implement the initializingbean interface

Implementing the initializingbean interface will implement the afterpropertiesset method, which will be called automatically. But this approach is invasive. Generally, it is not recommended to use.

Implement the afterpropertiesset method

Configuration XML

result:

Destroy

Similarly, the above figure shows the process of bean destruction. Includes the disposablebean interface.

Using the destroy method method

Configure bean

Configure loader

result:

Implement the disposablebean interface

Implement the disposablebean interface

configuration file

Scope of spring bean

Configuration example

Use method injection to coordinate beans with different scopes

Normally, if the singleton scope depends on the singleton scope. That is, the same object is obtained every time. Similarly, the prototype scope depends on the prototype scope, and new objects are obtained every time. However, if singleton depends on the prototype scope, the prototype in singleton is created for the first time every time. How to coordinate this relationship. Make sure what you get is correct every time.

In this case, spring provides a lookup method to solve this problem.

First, we define a prototype:

Then inject through the interface:

Configure a single instance:

Profile:

Load profile:

result:

As can be seen from the result diagram above, the objects generated in the previous way are the same every time. Injection through lookup is different each time. Can solve this problem. But is there a simpler way to feel the advantages and troubles of this way.

Make bean aware of spring container

Implement beannameaware and set the ID value by yourself.

Implement beanfactoryaware and applicationcontextaware aware aware spring container. Get the spring container.

Spring internationalization support

Configuration profile

New Chinese profile

message_ zh_ CN. properties:

New English profile

message_ en_ US. properties:

Load profile

result

summary

Well, the above is the whole content of this article. I hope the content of this article can bring some help to your study or work. If you have any questions, you can leave a message. Thank you for your support for programming tips.