前言

当我们想把配置的内容,动态赋值到某个配置类上的时候,可以使用@EnableConfigurationProperties + @ConfigurationProperties注解

代码准备

创建配置文件prop.properties

name=ada
age=18
email=123@qq.com

创建配置类

@ComponentScan("com.test.pops")
@PropertySource("classpath:prop.properties")
public class AppConfig {

}

创建启动类

public class Main {

    public static void main(String[] args) {

        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
    }
}

查看@ConfigurationProperties源码

@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Indexed
public @interface ConfigurationProperties {

	/**
	 * The prefix of the properties that are valid to bind to this object. Synonym for
	 * {@link #prefix()}. A valid prefix is defined by one or more words separated with
	 * dots (e.g. {@code "acme.system.feature"}).
	 * @return the prefix of the properties to bind
	 */
	@AliasFor("prefix")
	String value() default "";

	/**
	 * The prefix of the properties that are valid to bind to this object. Synonym for
	 * {@link #value()}. A valid prefix is defined by one or more words separated with
	 * dots (e.g. {@code "acme.system.feature"}).
	 * @return the prefix of the properties to bind
	 */
	@AliasFor("value")
	String prefix() default "";

	/**
	 * Flag to indicate that when binding to this object invalid fields should be ignored.
	 * Invalid means invalid according to the binder that is used, and usually this means
	 * fields of the wrong type (or that cannot be coerced into the correct type).
	 * @return the flag value (default false)
	 */
	boolean ignoreInvalidFields() default false;

	/**
	 * Flag to indicate that when binding to this object unknown fields should be ignored.
	 * An unknown field could be a sign of a mistake in the Properties.
	 * @return the flag value (default true)
	 */
	boolean ignoreUnknownFields() default true;

}

由源码我们可以得知这个注解可以作用于类上,作用于方法上

作用于类上

@EnableConfigurationProperties注解不指定value

创建TypeConfig

@ConfigurationProperties
@Component
public class TypeConfig {

    private String name;

    private Integer age;

    private String email;


    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;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

配置类不指定value 

@ComponentScan("com.test.pops")
@PropertySource("classpath:prop.properties")
@EnableConfigurationProperties
public class AppConfig {

}

运行main方法,查看运行结果

@EnableConfigurationProperties注解指定value

TypeConfig去除@Component注解

@ConfigurationProperties
public class TypeConfig {

    private String name;

    private Integer age;

    private String email;


    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;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

配置类指定value

@ComponentScan("com.test.pops")
@PropertySource("classpath:prop.properties")
@EnableConfigurationProperties({TypeConfig.class})
public class AppConfig {

}

运行main方法,查看运行结果 

@ConfigurationProperties设置prefix

改造TypeConfig

@ConfigurationProperties(prefix = "prop")
public class TypeConfig {

    private String name;

    private Integer age;

    private String email;


    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;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

修改配置文件prop.properties

name=ada
age=18
email=123@qq.com

prop.name=tom
prop.age=17
prop.email=456@qq.com

运行main方法,查看运行结果 

使用@ConstructorBinding注解绑定到构造器上

改造TypeConfig

@ConfigurationProperties(prefix = "prop")
public class TypeConfig {

    private String name;

    private Integer age;

    private String email;

    public TypeConfig() {
    }

    @ConstructorBinding
    public TypeConfig(String name, Integer age, String email) {
        this.name = name;
        this.age = age;
        this.email = email;
    }
}

运行main方法,查看运行结果 

PS : @ConstructorBinding注解只能在@EnableConfigurationProperties注解指定value的时候使用

作用于方法上

修改配置类prop.properties

name=ada
age=18
email=123@qq.com

prop.name=tom
prop.age=17
prop.email=456@qq.com

method.name=bob
method.age=16
method.email=789@qq.com

创建MethodConfig

@Configuration
public class MethodConfig {

    @Bean
    @ConfigurationProperties(prefix = "method")
    public Person person() {
        return new Person();
    }

    public static class Person {
        private String name;

        private Integer age;

        private String email;

        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;
        }

        public String getEmail() {
            return email;
        }

        public void setEmail(String email) {
            this.email = email;
        }
    }
}

运行main方法,查看运行结果