3. Bean scope and life cycle

Table of Contents

Scope Definition

6 Scopes of Beans

Bean Execution Process

Bean Lifecycle

Execution process

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Scope Definition

The scope of a Bean refers to a certain behavior pattern of the Bean in the entire Spring framework, such as the singleton singleton scope, which means that there is only one copy of the Bean in the entire Spring, and it is globally shared, so when other people modify itAfter reading this value, what another person reads is the modified value.

6 scopes of beans

When the Spring container initializes an instance of a bean, it also specifies the scope of the instance.Spring has 6 scopes, the last four are based on Spring MVC:

\1. singleton: singleton scope --> Spring selects this scope by default

\2. prototype: prototype scope (multiple instance scope)

                     instance.

\3. request: request scope (a request-response scope)

\4. session: session scope (a session scope)

\5. application: global scope (understand)

\6. websocket: HTTP WebSocket scope (understand)

Note: The last four states are values ​​in Spring MVC, and there are only the first two in a normal Spring project.

Bean execution process

Bean execution process (Spring execution process): start the Spring container -> instantiate the bean (allocate memory space, from scratch) -> register the bean in Spring (storage operation) -> assemble the bean to the required classin (fetch operation).

Bean Lifecycle

The life cycle of a bean is divided into the following 5 parts:

1. Instantiate Bean (allocate memory space for Bean, similar to new object)

2. Setting properties (Bean injection and assembly)

3.Bean initialization

3.1 implements various Aware notification methods, such as the interface methods of BeanNameAware, BeanFactoryAware, and ApplicationContextAware;

3.2 Execute BeanPostProcessor initialization pre-method;

3.3.1 Execute the @PostConstruct initialization method, which is executed after the dependency injection operation;

3.3.2 Execute the init-method method specified by yourself (if specified);

3.4 Execute the BeanPostProcessor initialization post method.

4. Use Bean

5. Destroy the Bean (the container can only be destroyed when the container is closed)

Execution process