@Autowiredと@Resourceの違いについて

• @Resourceは @Autowired + (@Qualifier)だと考えればいい
• Bean名とクラス名が同じ場合には違いはない
• Bean名とクラス名違う場合には以下のように書く

@Resource(name="testbean")
private ExampleService exampleService;

@Autowired
@Qualifier("testbean")
private ExampleService exampleService;

@Configuration and @Component and @Bean

Spring @Configuration vs @Component

• @Configuration
  • classをannotationすると、そのclassはcan be used by the Spring IoC container as a source of bean definitions.
  • springのcontextファイルだと考えればいい
• @Beanはbean
  • @Configurationはcontext xmlならその中のbean
• @Component
  • @ComponentScanによってbeanとして登録される
  • classに付けることが多いが、@Beanと同じレベルで考えればいい

Sample

@Configuration
public static class Config {

    @Bean
    public SimpleBean simpleBean() {
        return new SimpleBean();
    }

    @Bean
    public SimpleBeanConsumer simpleBeanConsumer() {
        return new SimpleBeanConsumer(simpleBean());
    }
}

間違った例

• 下の例はこれは完全にまちがい
• SimpleBeanConsumer will get a link to singleton SimpleBean. But unfortunately, it doesn’t work in signed enviroment.
• @Componentは @Beanと同じレベルのものconstructorでinitializeされるので、@Componentでなかで@Beanを使うのは間違い

// これは間違った例
@Component
public static class Config {

    @Bean
    public SimpleBean simpleBean() {
        return new SimpleBean();
    }

    @Bean
    public SimpleBeanConsumer simpleBeanConsumer() {
        return new SimpleBeanConsumer(simpleBean());
    }
}

@Componentを使うの場合にはこれがただしい

@Component
public static class Config {
    @Autowired
    SimpleBean simpleBean;

    @Bean
    public SimpleBean simpleBean() {
        return new SimpleBean();
    }

    @Bean
    public SimpleBeanConsumer simpleBeanConsumer() {
        return new SimpleBeanConsumer(simpleBean);
    }
}

conditionの種類

• class
• bean
• property
• resource
• web application
• SpEL

spring bootの @Conditional & @ConditionalOnXXX

http://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-auto-configuration.html

Class conditions

• @ConditionalOnClass
  • allows configuration to be included based on the presence of specific classes.
• @ConditionalOnMissingClass
  • allows configuration to be included based on the absence of specific classes.

Bean conditions

• @ConditionalOnBean
  • allow a bean to be included based on the presence of specific beans
• @ConditionalOnMissingBean
  • allow a bean to be included based on the absence of specific beans

Property conditions

@SpringBootApplication

これは以下の３つのannotationを合わせたもの

@Qualifier

@autowiredを利用する場合 同じinterfaceをもつ実装クラスが複数ある場合、どの実装クラスをinjectするかspringがわからなくなる。

http://javatechnology.net/spring/qualifier/

@Autowired
@Qualifier("testbean")
private ExampleService exampleService;

@RestController

• New from Spring 4
• 指定すると methodが domain objectをreturn
  • 通所は(@Controller)viewをreturn
• @Controller and @ResponseBodyの合体

@Scope

@Component、@Service、@Repository、@Controllerの違い

• 全部おなじ
• 役割を区分したいからだけ

@Value - プロパティファイルから設定を取得する

http://qiita.com/toshiro3/items/56a4d03658d31ef1f939

bean

package sample.spring.beans;

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

@Component
public class SampleBean {

    @Value("${sample.name}")
    private String name;

    @Value("${sample.age}")
    private int age;

    public String getMessage() {
        return String.format("Hello! My name is %s. I'm %d years old.", name, age);
    }

}

java config

package sample.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;

@Configuration
@ComponentScan
@PropertySource(value = {"classpath:beans.properties"})
public class AppConfig {

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

}

property file

sample.name = spring
sample.age = 11

unit test

package sample.spring.beans;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import sample.spring.AppConfig;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {AppConfig.class})
public class SampleBeanTest {

    @Autowired
    private SampleBean sampleBean;

    @Test
    public void greet() {
        System.out.println(sampleBean.getMessage());
    }

}

@PropertySource - Environmentを利用して取得する場合