【Spring】SpringBoot官方笔记2使用¶
Build Systems¶
选择Maven or Gradle，而不要Ant（not particularly well supported）
In practice, you do not need to provide a version for any of these dependencies (spring-boot-dependencies) in your build configuration, as Spring Boot manages that for you. When you upgrade Spring Boot itself, these dependencies are upgraded as well in a consistent way.
Each release of Spring Boot is associated with a base version of the Spring Framework.
Starters are a set of convenient dependency descriptors that you can include in your application.
starter命名区别：
official
spring-boot-starter-*third-party
thirdpartyproject-spring-boot-starter
Structuring¶
We generally recommend that you locate your main application class in a root package above other classes.
com
+- example
+- myapplication
+- MyApplication.java
|
+- customer
| +- Customer.java
| +- CustomerController.java
| +- CustomerService.java
| +- CustomerRepository.java
|
+- order
+- Order.java
+- OrderController.java
+- OrderService.java
+- OrderRepository.java
实际项目见得多的是controller、service这样的package，然后里面放多个文件。
Configuration¶
Although it is possible to use SpringApplication with XML sources,
we generally recommend that your primary source be a
single @Configuration class.
The @Import annotation can be used to import additional
configuration classes. Alternatively, you can use @ComponentScan to
automatically pick up all Spring components,
including @Configuration classes.
（因为@SpringBootApplication包含了@ComponentScan，所以能自动扫到@Configuration的配置类）
@ImportResource annotation to load XML configuration files.
Auto-configuration¶
Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added.
For example, if HSQLDB is on your classpath, and you have not
manually configured any database connection beans, then Spring Boot
auto-configures an in-memory database. If you add your
own DataSource bean, the default embedded database support backs
away.
exclude auto-configuration：
①annotation
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class })
public class MyApplication {
}
If the class is not on the classpath, you can use
the excludeName attribute of the annotation and specify the fully
qualified name instead.
②property
spring.autoconfigure.exclude
Spring Beans and Dependency Injection¶
Spring Beans可以理解为功能模块
@ComponentScan to find beans，all of your application components
(@Component, @Service, @Repository, @Controller, and
others) are automatically registered as Spring Beans.
constructor injection：
import org.springframework.stereotype.Service;
@Service
public class MyAccountService implements AccountService {
private final RiskAssessor riskAssessor;
public MyAccountService(RiskAssessor riskAssessor) {
this.riskAssessor = riskAssessor;
}
// ...
}
If a bean has more than one constructor, you will need to mark the one
you want Spring to use with @Autowired:
import java.io.PrintStream;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class MyAccountService implements AccountService {
private final RiskAssessor riskAssessor;
private final PrintStream out;
@Autowired
public MyAccountService(RiskAssessor riskAssessor) {
this.riskAssessor = riskAssessor;
this.out = System.out;
}
public MyAccountService(RiskAssessor riskAssessor, PrintStream out) {
this.riskAssessor = riskAssessor;
this.out = out;
}
// ...
}
（更常见的做法是直接在类变量定义时使用@Autowired或@Resource，省去constructor）
@SpringBootApplication¶
@EnableAutoConfiguration: enable Spring Boot’s auto-configuration mechanism@ComponentScan: enable@Componentscan on the package where the application is located (see the best practices)@SpringBootConfiguration: enable registration of extra beans in the context or the import of additional configuration classes. An alternative to Spring’s standard@Configurationthat aids configuration detection in your integration tests.
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
// Same as @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan
@SpringBootApplication
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
}