24.7.3 Properties conversion

将外部应用配置绑定到@ConfigurationProperties beans时，Spring会尝试将属性强制转换为正确的类型。如果需要自定义类型转换器，你可以提供一个ConversionServicebean（bean id为conversionService），或自定义属性编辑器（通过CustomEditorConfigurerbean），或自定义Converters（bean定义时需要注解@ConfigurationPropertiesBinding）。

由于该bean在应用程序生命周期的早期就需要使用，所以确保限制你的ConversionService使用的依赖。通常，在创建时期任何你需要的依赖可能都没完全初始化。比较建议使用@ConfigurationPropertiesBinding方式

import org.junit.Test; 
import org.junit.runner.RunWith; 

import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.beans.factory.annotation.Value; 
import org.springframework.boot.bind.ConverterBindingTests.TestConfig; 
import org.springframework.boot.context.properties.ConfigurationProperties; 
import org.springframework.boot.context.properties.ConfigurationPropertiesBinding; 
import org.springframework.boot.context.properties.EnableConfigurationProperties; 
import org.springframework.boot.test.IntegrationTest; 
import org.springframework.boot.test.SpringApplicationConfiguration; 
import org.springframework.context.annotation.Bean; 
import org.springframework.context.annotation.Configuration; 
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer; 
import org.springframework.core.convert.converter.Converter; 
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; 

import static org.hamcrest.Matchers.is; 
import static org.junit.Assert.assertThat; 
@RunWith(SpringJUnit4ClassRunner.class) 
@SpringApplicationConfiguration(TestConfig.class) 
@IntegrationTest("foo=bar") 
public class ConverterBindingTests { 

 @Value("${foo:}") 
 private String foo; 

 @Autowired 
 private Wrapper properties; 

 @Test 
 public void overridingOfPropertiesOrderOfAtPropertySources() { 
  assertThat(this.properties.getFoo().getName(), is(this.foo)); 
 } 

 @Configuration 
 @EnableConfigurationProperties(Wrapper.class) 
 public static class TestConfig { 

  @Bean 
  @ConfigurationPropertiesBinding 
  public Converter<String, Foo> converter() { 
   return new Converter<String, ConverterBindingTests.Foo>() { 

    @Override 
    public Foo convert(String source) { 
     Foo foo = new Foo(); 
     foo.setName(source); 
     return foo; 
    } 
   }; 
  } 

  @Bean 
  public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() { 
   return new PropertySourcesPlaceholderConfigurer(); 
  } 

 } 

 public static class Foo { 

  private String name; 

  public String getName() { 
   return this.name; 
  } 

  public void setName(String name) { 
   this.name = name; 
  } 

 } 

 @ConfigurationProperties 
 public static class Wrapper { 

  private Foo foo; 

  public Foo getFoo() { 
   return this.foo; 
  } 

  public void setFoo(Foo foo) { 
   this.foo = foo; 
  } 

 } 

}