《Spring注解驱动开发》第22章：使用@Value注解为bean的属性赋值

package org.springframework.beans.factory.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Value {
	String value();
}

@Value("normal")
private String normal; // 注入普通字符串

@Value("#{systemProperties['os.name']}")
private String systemPropertiesName; // 注入操作系统属性

@Value("#{ T(java.lang.Math).random() * 100.0 }")
private double randomNumber; //注入表达式结果

@Value("#{person.name}")
private String name; // 注入其他Bean属性：注入person对象的属性name

@Value("classpath:io/mykit/spring/config/config.properties")
private Resource resourceFile; // 注入文件资源

@Value("http://www.baidu.com")
private Resource url; // 注入URL资源

@Component
// 引入外部配置文件组：${app.configinject}的值来自config.properties。
// 如果相同
@PropertySource({"classpath:io/mykit/spring/config/config.properties",
    "classpath:io/mykit/spring/config/config_${anotherfile.configinject}.properties"})
public class ConfigurationFileInject{
    // 这里的值来自application.properties，spring boot启动时默认加载此文件
    @Value("${app.name}")
    private String appName; 

    // 注入第一个配置外部文件属性
    @Value("${book.name}")
    private String bookName; 

    // 注入第二个配置外部文件属性
    @Value("${book.name.placeholder}")
    private String bookNamePlaceholder; 

    // 注入环境变量对象，存储注入的属性值
    @Autowired
    private Environment env;  

    public String toString(){
        StringBuilder sb = new StringBuilder();
        sb.append("bookName=").append(bookName).append("\r\n")
        .append("bookNamePlaceholder=").append(bookNamePlaceholder).append("\r\n")
        .append("appName=").append(appName).append("\r\n")
        .append("env=").append(env).append("\r\n")
        // 从eniroment中获取属性值
        .append("env=").append(env.getProperty("book.name.placeholder")).append("\r\n");
        return sb.toString();
    }   
}

@Component
@PropertySource({"classpath:io/mykit/spring/config/advance_value_inject.properties"})
public class AdvanceValueInject {
...
}

@Value("${author.name:binghe}")

@Value("${author.name:binghe}")
private String name;

// SpEL：调用字符串Hello World的concat方法
@Value("#{'Hello World'.concat('!')}")
private String helloWorld;

// SpEL: 调用字符串的getBytes方法，然后调用length属性
@Value("#{'Hello World'.bytes.length}")
private String helloWorldbytes;

// SpEL: 传入一个字符串，根据","切分后插入列表中， #{}和${}配置使用(注意单引号，注意不能反过来${}在外面，#{}在里面)
@Value("#{'${server.name}'.split(',')}")
private List<String> servers;

// SpEL: 注意不能反过来${}在外面，#{}在里面，这个会执行失败
@Value("${#{'HelloWorld'.concat('_')}}")
private List<String> servers2;

package io.mykit.spring.plugins.register.bean;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import java.io.Serializable;
/**
 * @author binghe
 * @version 1.0.0
 * @description 测试实体类
 */
@Data
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class Person implements Serializable {
    private static final long serialVersionUID = 7387479910468805194L;
    private String name;
    private Integer age;
}

package io.mykit.spring.plugins.register.config;
import io.mykit.spring.plugins.register.bean.Person;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
 * @author binghe
 * @version 1.0.0
 * @description 测试属性赋值
 */
@Configuration
public class PropertyValueConfig {
    @Bean
    public Person person(){
        return new Person();
    }
}

package io.mykit.spring.test;
import io.mykit.spring.plugins.register.config.PropertyValueConfig;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import java.util.Arrays;
/**
 * @author binghe
 * @version 1.0.0
 * @description 测试bean的生命周期
 */
public class PropertyValueTest {
    @Test
    public void testPropertyValue01(){
        //创建IOC容器
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(PropertyValueConfig.class);
        String[] names = context.getBeanDefinitionNames();
        Arrays.stream(names).forEach(System.out::println);
    }
}

org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
propertyValueConfig
person

package io.mykit.spring.test;
import io.mykit.spring.plugins.register.bean.Person;
import io.mykit.spring.plugins.register.config.PropertyValueConfig;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import java.util.Arrays;
/**
 * @author binghe
 * @version 1.0.0
 * @description 测试bean的生命周期
 */
public class PropertyValueTest {
    @Test
    public void testPropertyValue01(){
        //创建IOC容器
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(PropertyValueConfig.class);
        String[] names = context.getBeanDefinitionNames();
        Arrays.stream(names).forEach(System.out::println);

        System.out.println("================================");
        Person person = (Person) context.getBean("person");
        System.out.println(person);
    }
}

package io.mykit.spring.plugins.register.bean;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import org.springframework.beans.factory.annotation.Value;
import java.io.Serializable;
/**
 * @author binghe
 * @version 1.0.0
 * @description 测试实体类
 */
@Data
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class Person implements Serializable {
    private static final long serialVersionUID = 7387479910468805194L;
    @Value("binghe")
    private String name;
    @Value("#{20-2}")
    private Integer age;
}