通过配置文件来赋值有两个注解

@Value

@ConfigurationProperties

@Value如何注入值

package com.springboot.helloword.configuration;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;
@Configuration
@PropertySource("classpath:jdbc.properties")
public class JdbcConfig {
    DruidDataSource dataSource=null;
    @Value("${jdbc.driverClassName}")
    String driverClassName;
    @Value("${jdbc.url}")
    String url;
    @Value("${jdbc.username}")
    String username;
    @Value("${jdbc。password}")
    String password;
@Bean
    public DataSource dataSource(){
        new DruidDataSource();
        dataSource.setDriverClassName(driverClassName);
        dataSource.setUrl(url);
        dataSource.setName(username);
        dataSource.setPassword(password);
        return dataSource();

    }
}

代码部分注解的解释

@Configuration

1. 写在类上

2. 表示这个类是一个配置类

@PropertySource("classpath:jdbc.properties)

1. 相当于springboot中使用标签引入外部属性文件<context:property-placeholder location="classpath:jdbc.properties"/>

2. 写在类上

@Bean

1. 将方法的返回值注入到bean 容器中 容器组件的id默认是方法名

2. 写在方法上

@Value

1. 用于配置文件值的注入

2. 建议写在属性名上

3. @Value相当于<bean> <properties name="" value></properties></bean>

Jdbc.Properties

jdbc.driverClassName=com。mysql。jdbc。Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/springboot
jdbc.username=root
jdbc.password=root

@Configuration值的注入

kage com.springboot.helloword.pojo;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

import javax.xml.crypto.Data;
import java.util.List;
import java.util.Map;
@Component
@ConfigurationProperties(prefix="person")
public class Person {

    private String lastName;
    private Integer age;
    private boolean boss;
    private Data birth;
    private Map<String,Object> maps;
    private List<Object> lists;
    private Dog dog;

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public void setBoss(boolean boss) {
        this.boss = boss;
    }

    public void setBirth(Data birth) {
        this.birth = birth;
    }

    public void setMaps(Map<String, Object> maps) {
        this.maps = maps;
    }

    public void setLists(List<Object> lists) {
        this.lists = lists;
    }

    public void setDog(Dog dog) {
        this.dog = dog;
    }

    public String getLastName() {
        return lastName;
    }

    public Integer getAge() {
        return age;
    }

    public boolean isBoss() {
        return boss;
    }

    public Data getBirth() {
        return birth;
    }

    public Map<String, Object> getMaps() {
        return maps;
    }

    public List<Object> getLists() {
        return lists;
    }

    public Dog getDog() {
        return dog;
    }

}

application.yml

server:
  port:8081
person:
  lastName:小谎言
    age: 18
    boss: false
    birth: 2017/12/12
    maps: {k1: v1, k2: 12}
    lists:
      - lisi
      - zhaoliu
    dog:
      name: 小狗
      age: 14

@ConfigurationProperties(prefix="")

告诉springboot本类中所有的属性和配置文件相关的配置进行绑定

写在类上

总结：

要想用@ConfigurationProperties（prefix=“”）

1. yml文件要与@ConfigurationProperties下的类的属性值一一对应

2. 如果需要@ConfigurationProperties(prefic="")有提示，可以在pom中加入spring-boot-configuration-processor。

3. @ ComPonent是为了解决@ConfigurationProperties爆红的问题

4. @ConfigurationProperties下的类的属性值必须要有get set 方法

5. 与@Bean结合为属性赋值

6. 与@PropertySource（只能用于properties文件）结合读取指定文件

@Value与@ConfigurationProperties的比较

配置文件yml还是properties他们都能获取值

只有某个业务，单个属性@Value

专门编写一个JavaBean来和配置文件进行映射，我们使用@ConfigurationProperties