SpringBoot 01: JavaConfig + @ImportResource + @PropertyResource

springboot的前置知识:通过注解创建对象和读取配置文件

1. JavaConfig

设计思想

  • 使用java类作为xml配置文件的替代,是配置spring容器的纯java的方式
  • 可以创建java对象并把对象注入到spring容器中

注解实现

  • @Configuration : 放在一个类的上面,表示这个类是作为配置文件使用的
  • @Bean:放在返回值是对象的方法上,容器启动时,声明对象,并把对象注入到容器中
  • 上面两个注解配套使用

代码实现

package com.example.springboot.configuration;

import com.example.springboot.model.Student;
import org.springframework.context.annotation.*;

@Configuration
public class SpringConfig {
    @Bean
    public Student getStudent(){
        Student student = new Student();
        student.setName("橘子");
        student.setAge(18);
        return student;
    }

    @Bean(name = "student")
    public Student getStudentByBeanName(){
        Student student = new Student();
        student.setName("饺子");
        student.setAge(21);
        return student;
    }
}

测试代码

package com.example.springboot.testspringconfig;

import com.example.springboot.configuration.SpringConfig;
import com.example.springboot.model.Student;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class TestSpringConfig {
    @Test
    public void testSpringConfig(){
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringConfig.class);
        Student student = (Student) applicationContext.getBean("student");
        //未在@Bean中指定对象名称时,从方法名(小驼峰命名规范)来获取对象
        //Student student = (Student) applicationContext.getBean("getStudent");
        System.out.println("获取到的对象: " + student);
    }
}

2. @ImportResource

设计思想

  • 导入其他的xml配置文件, 等于在xml 使用如下import标签
<import resources="其他配置文件"/>

代码实现

  • SpringConfig类
package com.example.springboot.configuration;

import org.springframework.context.annotation.*;

@ImportResource(value = "classpath:applicationContext.xml")
public class SpringConfig {

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

    <bean id="cat" class="com.example.springboot.model.Cat">
        <property name="catCard" value="0010"/>
        <property name="catName" value="tomcat"/>
    </bean>
</beans>

测试代码

package com.example.springboot.testspringconfig;

import com.example.springboot.configuration.SpringConfig;
import com.example.springboot.model.Cat;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class TestSpringConfig {
    @Test
    public void testImportResource(){
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringConfig.class);
        Cat cat = (Cat) applicationContext.getBean("cat");
        System.out.println("获取到的对象: " + cat);
    }
}

3. @PropertyResource

设计思想

  • 读取properties属性配置文件,使用属性配置文件可以实现外部化配置

使用步骤

  • 在resources目录下,创建properties文件, 使用 key=value 的格式提供数据
  • 在@PropertyResource 指定properties文件的位置
  • 使用在待注入值的变量上使用@Value(value=”${key}”)

需要用的其他注解

  • @Component:用在实体类上
  • @ComponentScan:SpringConfig类上
  • @Value:待注入值的属性上

代码实现

  • SpringConfig类
package com.example.springboot.configuration;

import com.example.springboot.model.Student;
import org.springframework.context.annotation.*;

@PropertySource(value = "classpath:food.properties")
@ComponentScan(basePackages = "com.example.springboot.model")
public class SpringConfig {
}
  • food.properties
food.name=饺子
food.price=13
  • JiaoZi类
package com.example.springboot.model;

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

@Component("jiaozi")
public class JiaoZi {
    
   @Value("${food.name}")
    private String name;
   @Value("${food.price}")
    private double price;

    @Override
    public String toString() {
        return "JiaoZi{" +
                "name='" + name + '\'' +
                ", price=" + price +
                '}';
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public JiaoZi(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public JiaoZi() {
    }
}

测试代码

package com.example.springboot.testspringconfig;

import com.example.springboot.configuration.SpringConfig;
import com.example.springboot.model.JiaoZi;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class TestSpringConfig {
    
    @Test
    public void testPropertiesSource(){
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringConfig.class);
        JiaoZi jiaoZi = (JiaoZi) applicationContext.getBean("jiaozi");
        System.out.println("food: " + jiaoZi);
    }
}