SpringBoot/Spring使用@Value进行属性绑定（尚硅谷）

接上篇：springboot使用ConfigurationProperties注解读取自定义属性（传智播客代码）

部分代码参考上篇，这里用@Value读取值

1、@Value读取数据

@Value支持字面量、Spring EL表达式(#),美元符号($)，相比于@ConfigurationProperties,他用$取值时需要完全路径

package com.atguigu.bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import java.util.Date;
import java.util.List;
import java.util.Map;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Component
public class Person {

    /***
     * 美元表达式(从配置文件、系统环境变量读取)
     */
    @Value("${person.lastName}")
    private String lastName;

    /***
     * Spring EL表达式
     */
    @Value("#{11*2}")
    private Integer age;

    /***
     * 字面量
     */ 
    @Value("true")
    private Boolean boss;
    private Date birth;

    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;
}

 2、ConfigurationProperties注解JSR303数据校验

package com.atguigu.bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
import org.springframework.validation.annotation.Validated;

import javax.validation.constraints.Email;
import java.util.Date;
import java.util.List;
import java.util.Map;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Component
@ConfigurationProperties(prefix = "person")
@Validated
public class Person {

    @Email
    private String lastName;
    private Integer age;
    private Boolean boss;
    private Date birth;

    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;
}

由于lastName不是有效的邮箱，启动时即报错

Binding to target org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'person' to com.atguigu.bean.Person failed:

    Property: person.lastName
    Value: zhangsan
    Origin: class path resource [application.properties]:2:17
    Reason: 不是一个合法的电子邮件地址

3、@Value不支持复合数据类型绑定

测试用例

package com.atguigu;

import com.atguigu.bean.Person;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.List;
import java.util.Map;

@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
class DemoApplicationTests {

    @Autowired
    Person person;

    @Test
    void customPropertiesTest()
    {
        log.info("{}",person);
    }
}

3.1、 $（美元符号读取map直接报错）

package com.atguigu.bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import org.springframework.validation.annotation.Validated;

import java.util.Date;
import java.util.List;
import java.util.Map;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Component
public class Person {

    /***
     * 美元表达式(从配置文件、系统环境变量读取)
     */
    @Value("${person.lastName}")
    private String lastName;

    /***
     * Spring EL表达式
     */
    @Value("#{11*2}")
    private Integer age;

    /***
     * 字面量
     */ 
    @Value("true")
    private Boolean boss;
    private Date birth;

    @Value("${person.maps}")
    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;
}

3、2使用spring el表达式获取不到值

package com.atguigu.bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import org.springframework.validation.annotation.Validated;

import java.util.Date;
import java.util.List;
import java.util.Map;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Component
public class Person {

    /***
     * 美元表达式(从配置文件、系统环境变量读取)
     */
    @Value("${person.lastName}")
    private String lastName;

    /***
     * Spring EL表达式
     */
    @Value("#{11*2}")
    private Integer age;

    /***
     * 字面量
     */ 
    @Value("true")
    private Boolean boss;
    private Date birth;

    @Value("#{person.maps}")
    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;
}

4、@ConfigurationProperties和@Value使用场景区别