Spring framework study notes 3: Use annotations instead of configuration files, spring Study Notes

Spring framework study notes 3: Use annotations instead of configuration files, spring Study Notes

1. Import context constraint: spring-context-4.2.xsd

 

2. Open the xml configuration file in design mode, right-click edit namespaces, and click add to add

 

 

After completion, it should be like this:

 

In the configuration file, write as follows:

<?xml version="1.0" encoding="UTF-8"?><beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd ">    <context:component-scan base-package="bean"></context:component-scan></beans>

 

Use annotations in the class as follows:

Package bean; import javax. annotation. postConstruct; import javax. annotation. preDestroy; import javax. annotation. resource; import org. junit. validator. publicClassValidator; import org. springframework. beans. factory. annotation. autowired; import org. springframework. beans. factory. annotation. qualifier; import org. springframework. beans. factory. annotation. value; import org. springframework. context. annotation. scope; import org. springframework. stereotype. component; import org. springframework. stereotype. controller; import org. springframework. stereotype. repository; import org. springframework. stereotype. service; // the content of the configuration file <bean name = "user" class = "bean. user "/> // @ Component (" user ") // The four types are essentially the same. To facilitate understanding, we recommend that you use the following three types of // @ Service (" user ") // use the service layer // @ Controller ("user") // use the web layer @ Repository ("user ") // use the dao layer // specify the Scope of action of the object @ Scope (scopeName = "singleton") public class User {@ Value ("Tom") // assign a Value to private String name; private Integer age; // @ Autowired // object assignment, automatic assembly // problem: if multiple objects of the same type are involved, @ Resource (name = "car") cannot be distinguished ") // this method can explicitly specify (recommended) private Car; public car getCar () {return Car;} public void setCar (car Car) {this. car = car;} public String getName () {return name;} public void setName (String name) {this. name = name;} public Integer getAge () {return age;} @ Value ("20") // you can assign a Value in the set method. The effect is the same, but does not destroy encapsulation public void setAge (Integer age) {this. age = age ;}@ Override public String toString () {return "User [name =" + name + ", age =" + age + ", car = "+ car +"] ";}@ PostConstruct // initialization method when the init-mothod public void init () {System. out. println ("initialization") ;}@ PreDestroy // destroy method public void destory () {System. out. println ("Destroy ");}}

 

Car class:

package bean;import org.springframework.beans.factory.annotation.Value;import org.springframework.stereotype.Component;@Component("car")public class Car {    @Value("car2")    private String  name;    private String color;        public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getColor() {        return color;    }    public void setColor(String color) {        this.color = color;    }    @Override    public String toString() {        return "Car [name=" + name + ", color=" + color + "]";    }        }