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We must first understand what is the inversion of control and dependency injection.
Contrast concept:
| Inversion of Control | DI (dependency injection) dependency injection |
| meaning: The principle in this way converted into new objects, spring way to create objects through reflection. spring to create a finished object into a container, who needs who gave injected into it. Simply put: the right to create objects and managed objects to the spring |
Meaning: is to set the value of the property to the object. Property is set to the value of the original object: set value method to set the target to the object constructor initializes the time setting. |
| Creating objects
|
Set the object attribute value |
Inversion of Control:
1. Create an object in several ways?
Constructor
static factory
instance factory
2.spring create objects range
Problem: every acquisition target time, spring is to create a new object or give us always return the same object?
Singleton: only one object in memory, each time the address is acquired as the value of the object.
Many cases of: Memory Each object is a new object, their address values are different.
Answer: The object created by default under the spring are a single case (the object each time returned are the same).
3.spring create an object life cycle
When an object is created to create spring, when to run, when to be destroyed.?
1. Create and configuration file loading time
2. Run, when to use the object
3. Destruction, spring, when the container is closed
Dependency Injection:
1. Fill the ways dependent?
attribute set provided
configured injection mode
p c namespace namespace injection and injection
complex data type injection
Common notes:
| Notes name | effect |
| @Component @Component("abc") |
The default id is the class name first letter lowercase Manually specified <bean id = "abc" class = "xxxx"> |
| @Controller | Determining a presentation layer / control layer using the Controller |
| @Service | Business logic using Service |
| @Repository | Using the Repository persistence layer dao |
| @Autowired |
Automatic annotation |
| @Qualifier("id") | 1 :( bean id injection manner according to the specified values) |
| @Value("#{son1}") | Injection method 2: |
| @Resource(name="son1") | Injection method 3: jdk injection |