spring学习---3

1.装配进阶

1)environment-specific bean

@profile

@Configuration
public class DataSourceConfig {
@Bean(destroyMethod="shutdown")
@Profile("dev")
public DataSource embeddedDataSource() {
return new EmbeddedDatabaseBuilder()
.setType(EmbeddedDatabaseType.H2)
.addScript("classpath:schema.sql")
.addScript("classpath:test-data.sql")
.build();
}
@Bean
@Profile("prod")
public DataSource jndiDataSource() {
JndiObjectFactoryBean jndiObjectFactoryBean =
new JndiObjectFactoryBean();
jndiObjectFactoryBean.setJndiName("jdbc/myDS");
jndiObjectFactoryBean.setResourceRef(true);
jndiObjectFactoryBean.setProxyInterface(javax.sql.DataSource.class);
return (DataSource) jndiObjectFactoryBean.getObject();
}
}

2）conditioinal beans

@Conditional

@Bean
@Conditional(MagicExistsCondition.class)
public MagicBean magicBean() {
return new MagicBean();
}

3）ambiguity in autowiring

autowiring works when exactly one bean matches the disired result.

@ Primary--- designating a primary bean

@Qualifier("beanid")

4)Scoping beans

在spring的应用上下文中，所有的bean都是单例的

@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)

 Singleton—One instance of the bean is created for the entire application.
 Prototype—One instance of the bean is created every time the bean is injected
into or retrieved from the Spring application context.
 Session—In a web application, one instance of the bean is created for each session.
 Request—In a web application, one instance of the bean is created for each
request.

5）runtime value injection

@Configuration
@PropertySource("classpath:/com/soundsystem/app.properties")
public class ExpressiveConfig {
@Autowired
Environment env;
@Bean
public BlankDisc disc() {
return new BlankDisc(
env.getProperty("disc.title"),
env.getProperty("disc.artist"));
}
}

6) wiring with Spring Expression Language(SpEL)

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