SpringIOC-注入的方式

作者: do_young | 来源:发表于2019-01-03 13:59 被阅读17次

前言

为了方便对各个注入方式写例子，自己创建了一个工程。

创建一个spring工程

首先创建一个maven工程，引入spring-context包，我这里使用的是4.3.12.RELAESE版本。

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.12.RELEASE</version>
        </dependency>
    </dependencies>

根据依赖关系，会引入以下的spring包。

spring-context.png

方法一：基于xml

创建一个pojo对象User

package com.going.spring.bean;

public class User {
    
    private String name;
    private Integer age;
    private String nickName;
    
    public String getNickName() {
        return nickName;
    }
    public void setNickName(String nickName) {
        this.nickName = nickName;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    
    public User(String name, Integer age, String nikeName) {
        super();
        this.name = name;
        this.age = age;
        this.nickName = nikeName;
    }
    public User() {
        super();
    }
    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", nickName=" + nickName + "]";
    }
}

创建一个xml配置文件beans-user.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd">

    <bean id="user" class="com.going.spring.bean.User"  >
        <property name="age" value="1"></property>
        <property name="name" value="doyoung"></property>
        <property name="nickName" value="doyoungdy"></property>
    </bean>
    
</beans>

测试类

package com.going.spring.bean;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class UserXmlIocTest extends User {
    @Test
    public void test() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans-user.xml");
        User user = (User) applicationContext.getBean("user");
        System.out.println(user);
    }
}

方法二：基于注解

对POJO对象添加注解

package com.going.spring.bean.anno;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class UserAnno {
    @Value("doyoung")
    private String name;
    @Value("21")
    private Integer age;
    @Value("doyoungdy")
    private String nickName;
    
    public String getNickName() {
        return nickName;
    }
    public void setNickName(String nickName) {
        this.nickName = nickName;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    
    public UserAnno(String name, Integer age, String nikeName) {
        super();
        this.name = name;
        this.age = age;
        this.nickName = nikeName;
    }
    public UserAnno() {
        super();
    }
    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", nickName=" + nickName + "]";
    }
}

创建一个xml配置文件beans-useranno.xml，指定加载配置注解类的路径

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd">

    <context:component-scan base-package="com.going.spring.bean.anno" ></context:component-scan>
    
</beans>

注：当然也可以使用配置类使用@ComponentScans注解来做相同的配置。

测试类

package com.going.spring.bean;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.going.spring.bean.anno.UserAnno;

public class UserAnnoIocTest extends User {
    @Test
    public void test() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans-useranno.xml");
        UserAnno user = (UserAnno) applicationContext.getBean(UserAnno.class);
        System.out.println(user);
    }
}

方法三：基于配置类

创建一个配置类

说明在当前ioc容器中，当需要一个User对象的时候，就通过配置类中的user方法，创建一个User对象。

package com.going.spring.bean.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.going.spring.bean.User;

@Configuration
public class UserAnnoConfig {
    //给容器中注册一个Bean;类型为返回值的类型，id默认是用方法名作为id
    @Bean("user")
    public User user(){
        return new User("doyoung", 23, "doyoungdy");
    }
}

测试类

通过AnnotationConfigApplicationContext类创建一个Spring的容器，在参数中配置对应的配置类。

package com.going.spring.bean;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.going.spring.bean.config.UserAnnoConfig;

public class UserConfiglIocTest extends User {

    @Test
    public void test() {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(UserAnnoConfig.class);
        User user = (User) applicationContext.getBean("user");
        System.out.println(user);
        
    }

}

(注：其实配置类也可以归类于基于注解的方法。

方法四：@Import标签

可以直接使用Import标签，在里面配置需要注入的类，如：

@Configuration
@Import({User.class, UserAnno.class})
public class UserImportConfig {
}

方法五：@Import标签+ImportSelector接口

实现一个ImportSelector接口：

import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

import com.going.spring.bean.User;
import com.going.spring.bean.anno.UserAnno;

public class UserImportSelector implements ImportSelector {
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{User.class.getName(),UserAnno.class.getName()};
    }
}

将ImportSelector接口的实现类配置在@Import注解中：

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

@Configuration
@Import({UserImportSelector.class})
public class UserImportConfig2 {
}

方法六：@Import标签+ImportBeanDefinitionRegistrar接口

实现一个ImportBeanDefinitionRegistrar接口：

import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

import com.going.spring.bean.User;
import com.going.spring.bean.anno.UserAnno;

public class UserBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        RootBeanDefinition beanDefinition = new RootBeanDefinition(User.class);
        registry.registerBeanDefinition("user", beanDefinition);
        beanDefinition = new RootBeanDefinition(UserAnno.class);
        registry.registerBeanDefinition("userAnno", beanDefinition);
    }
}

将ImportBeanDefinitionRegistrar 接口的实现类配置在@Import注解中：

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

@Configuration
@Import({UserBeanDefinitionRegistrar.class})
public class UserImportConfig3 {
}

方法七：FactoryBean

实现一个FactoryBean接口：

import org.springframework.beans.factory.FactoryBean;
import com.going.spring.bean.User;

public class UserFactoryBean implements FactoryBean<User> {

    public User getObject() throws Exception {
        return new User();
    }

    public Class<?> getObjectType() {
        return User.class;
    }

    public boolean isSingleton() {
        return false;
    }
}

通过配置类将UserFactoryBean注入到容器中：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class UserImportConfig4 {
    
    @Bean
    public UserFactoryBean colorFactoryBean(){
        return new UserFactoryBean();
    }
}

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