spring authentication -- 2 -- dependency injection

Keywords: Java Spring

catalogue

One dependency injection

1 what is dependency injection

2 @Bean injection

2.1 test the function of @ Bean component injection:

2.2 during spring IOC component injection, the component is automatically matched by type and Bean Id

3 @Autowired auto assembly (wiring)

four set method injection (Bean attribute injection)

One dependency injection

1 what is dependency injection

2 @Bean injection

The Spring IOC container provides the dependency injection function, which can inject a component dependent object into the appropriate location before use. For example, the following relationship simulates the dependency chainsaw when a bald head forcibly cuts a tree

Spring IOC solves dependency injection by adding parameters to the Bean component initialization method in the configuration class Config. During initialization, the spring IOC container will automatically inject Bean component objects according to the type to solve the problem of "dependency injection":

2.1 test the function of @ Bean component injection:

Step 1: create a new spring2 project and add dependencies to the pom file

 <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.2.RELEASE</version>
        </dependency>
        <!--JUnit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>
        <!---->
        <dependency>
            <groupId>javax.annotation</groupId>
            <artifactId>javax.annotation-api</artifactId>
            <version>1.3.2</version>
        </dependency>
    </dependencies>

Step 2: create tool classes and workers under the demo package respectively,

package cn.tedu.demo;

import java.io.Serializable;

public class Saw implements Serializable {
    private String name = "Ice saw";

    @Override
    public String toString() {
        return name;
    }
}

package cn.tedu.demo;

import java.io.Serializable;

public class Worker implements Serializable {
    private String name = "Bald head strength";

    public Saw saw;

    public void work(){
        System.out.println(name+"use"+saw+"Cut down trees");
    }
}

Step 3: edit the configuration class and use @ Bean dependency injection to connect the two

package cn.tedu.context;

import cn.tedu.demo.Saw;
import cn.tedu.demo.Worker;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class Config {

    @Bean
    public Saw saw(){
        return new Saw();
    }
    /*Spring The type of Bean component is automatically matched according to the variable type
    * If the match is successful, the Bean component is injected into the method parameters*/
    @Bean
    public Worker worker(Saw s){//The parameter types should match correctly
        Worker worker = new Worker();
        worker.saw=s;
        return worker;
    }
}

Step 4: create a test class under the test package and view the results on the console

package cn.tedu.test;

import cn.tedu.context.Config;
import cn.tedu.demo.Worker;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class TestCase {
    AnnotationConfigApplicationContext ctx;
    @Before//initialization
    public void init(){
        ctx =new AnnotationConfigApplicationContext(Config.class);
    }

    @After//Destruction method
    public void destroy(){
        ctx.close();
    }

    @Test
    public void testWorker(){
        Worker worker = ctx.getBean("worker", Worker.class);
        worker.work();//A bald man cuts trees with an ice saw
    }
}

2.2 during spring IOC component injection, the component is automatically matched by type and Bean Id

3 @Autowired auto assembly (wiring)

The component scanning function provided by Spring can also complete dependency injection during scanning, which can reduce coding and improve programming efficiency

How do I use @ Autowired? Inject into the object attribute and set method, depending on the situation!!!

The following exercises are injected into object attributes:

Step 1: create a new project spring03, copy the src package of spring2, edit the tool class and worker respectively, and add the package scanning component to the configuration class

Step 2: the test class remains unchanged and the test results are the same. Therefore, adding component scanning and dependency injection can reduce code and improve programming efficiency