Spring Boot 从配置文件注入到自动配置（一）

SpringBoot使用一个全局的配置文件，配置文件名的

application.properties
application.yml
配置文件的作用 : SpringBoot底层都给我们配置好了，但有时候我们需要修改一些默认配置。
SpringBoot提供了简单的配置注入功能，可以为bean对象直接注入默认值。
以下是配置注入相关流程。

@ConfigurationProperties(prefix = "****")

1. 创建接收配置内容的实体

实体类 Person

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

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

/**
 * 将配置文件中的配置，映射到这个组件中
 * @ConfigurationProperties: 告诉SpringBoot将本类所有属性和配置文件中相关的配置进行绑定
 *      prefix = "person" : 配置文件中那个下面的所有属性进行一一映射
 * 只有这个这个组件是容器中的组件，才能使用容器提供的@ConfigurationProperties的功能
 */
@Component 
@ConfigurationProperties(prefix = "person")
public class Person {
    private String lastName;
    private Integer age;
    private Boolean boss;
    private Date birth;

    private Map<String , Object> map;
    private List<Object> list;
    private Dog dog;

    public String getLastName() {
        return lastName;
    }

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

    public Integer getAge() {
        return age;
    }

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

    public Boolean getBoss() {
        return boss;
    }

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

    public Date getBirth() {
        return birth;
    }

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

    public Map<String, Object> getMap() {
        return map;
    }

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

    public List<Object> getList() {
        return list;
    }

    public void setList(List<Object> list) {
        this.list = list;
    }

    public Dog getDog() {
        return dog;
    }

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

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder( "{\"Person\":{" );
        sb.append( "\"lastName\":\"" )
                .append( lastName ).append( '\"' );
        sb.append( ",\"age\":" )
                .append( age );
        sb.append( ",\"boss\":" )
                .append( boss );
        sb.append( ",\"birth\":\"" )
                .append( birth ).append( '\"' );
        sb.append( ",\"map\":" )
                .append( map );
        sb.append( ",\"list\":" )
                .append( list );
        sb.append( ",\"dog\":" )
                .append( dog );
        sb.append( "}}" );
        return sb.toString();
    }
}

实体类 Dog

public class Dog {

    private String name;
    private Integer age;

    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;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder( "{\"Dog\":{" );
        sb.append( "\"name\":\"" )
                .append( name ).append( '\"' );
        sb.append( ",\"age\":" )
                .append( age );
        sb.append( "}}" );
        return sb.toString();
    }
}

2.在配置文件中存入配置信息

application.yml

server:
  port: 8081

person:
  lastName: zhangsan # 也可写成(松散语法) last-name:zhansang
  age: 18
  boss: false
  birth: 2017/12/12
  map: {k1: v1, k2 : 12}
  list:
    - lisi
    - zhaoliu
  dog:
    name: 史努比
    age: 2

使用的时候通过自动注入可以获取默认的配置信息（从新new不会存在注入的配置信息！原因是没有赋值。@ConfigurationProperties做了那些工作就很清楚了。）。

@@Value( "${****.fieldName}" )

1.创建实体类

实体类 Cat

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

@Component
public class Cat {
    @Value( "${cat.name}" )
    private String name;
    @Value( "${cat.age}" )
    private Integer age;

    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;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder( "{\"Cat\":{" );
        sb.append( "\"name\":\"" )
                .append( name ).append( '\"' );
        sb.append( ",\"age\":" )
                .append( age );
        sb.append( "}}" );
        return sb.toString();
    }
}

2.在配置文件中存入配置信息

server:
  port: 8081

cat:
  name: Tom
  age: 5

@Value获取值和@ConfigurationProperties获取值比较