使用@EnableConfigurationProperties注冊配置Bean時的命名規則

Spring和Spring Boot開發中，常使用@ConfigurationProperties注解某個類，使其實例接受一組具有相同前綴的配置項。

可以使用@Component或Java Config將使用@ConfigurationProperties的類聲明為Bean。

Spring Boot提供了@EnableConfigurationProperties也可以實現類似的注冊功能。

然而@EnableConfigurationProperties注冊配置Bean時，設置的Bean名稱卻比較特別，有以下兩種情形。

1. @ConfigurationProperties#prefix 為空

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;

@Data
@ConfigurationProperties // @ConfigurationProperties#prefix沒有設置值的場景
public class AnotherBean {
    private String anotherAttr1;
    private String anotherAttr2;
    private String anotherAttr3;
}

此時application.properties的配置項不需要某個特定的前綴：

another-attr1 = av1
another-attr2 = av2
another-attr3 = av3

如果使用@EnableConfigurationProperties({AnotherBean.class})將其注冊為Bean時，其名字是：被@ConfigurationProperties注解的類的全類名：

import org.assertj.core.api.Assertions;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest(properties = {"another-attr1 = v1", "another-attr2 = aaavvv2", "another-attr3 = vvvaaa3"})
public class AnotherBeanTest {

    @Autowired
    private AnotherBean anotherBean;

    @Autowired
    private ApplicationContext context;

    @Test
    public void contextInitialized() {
        Assertions.assertThat(anotherBean).isNotNull();
        Assertions.assertThat(anotherBean.getAnotherAttr1()).isEqualToIgnoringCase("v1");
        Assertions.assertThat(anotherBean.getAnotherAttr2()).isEqualToIgnoringCase("aaavvv2");
        Assertions.assertThat(anotherBean.getAnotherAttr3()).isEqualToIgnoringCase("vvvaaa3");
    }

    @Test
    public void testCorrectName() {
        boolean f = context.containsBean("com.dw.sb.demo.bean.AnotherBean"); // 真實Bean名稱: 全類名
        Assertions.assertThat(f).isTrue();
    }

    @Test
    public void testErrorName() {
        boolean f = context.containsBean("anotherBean");
        Assertions.assertThat(f).isFalse();
    }
}

2. @ConfigurationProperties#prefix 不為空

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;

@Data
@ConfigurationProperties(prefix = "demo") // @ConfigurationProperties#prefix有值的場景
public class DemoBean {
    private String attr1;
    private String attr2;
}

此時配置項是很熟悉的情形，需要有共同的前綴，如：

demo.attr1 = value1
demo.attr2 = value2

如果使用@EnableConfigurationProperties({DemoBean.class})將其注冊為Bean，Bean的名字是

@ConfigurationProperties#prefix的值 + "-" + 注解類的全類名：

import org.assertj.core.api.Assertions;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class DemoBeanTest {

    @Autowired
    private ApplicationContext context;

    @Test
    public void testWrongName() {
        boolean f = context.containsBean("demoBean");
        Assertions.assertThat(f).isFalse();
    }

    @Test
    public void testCorrectName() {
        boolean f = context.containsBean("demo-com.dw.sb.demo.bean.DemoBean"); // 真實的Bean名稱："前綴-全類名"
        Assertions.assertThat(f).isTrue();
    }
}

源碼中，EnableConfigurationPropertiesImportSelector#ConfigurationPropertiesBeanRegistrar#getName方法實現了上述功能。

以上內容基於Spring Boot 2.0.6.RELEASE。