Spring Boot Note

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发布于：Sep 14, 2019

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Project that build with Maven

Quick buile a Spring Boot project

Use your IDE and new a project with Spring Initializer

Some basic operations

Creat an excutable jar

To create an excutable jar we neen to add the spring-boot-maven-plugin to our pom.xml.

Insert the following lines just below the dependencis section

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<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
		</plugin>
	</plugins>
</build>
```  
  
and than run

mvn package

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If you look in the `target` directory,you should see a JAR file.

To run the JAR use the `java -jar`command.

### Run with Maven Plugin

mvn spring-boot:run

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---

## About POM file
###1. <parent>
``` xml
<!-- example -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.8.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

Which is like the arbitration center of Spring Boot

###2. <dependencis>
This part is to import dependencis

starter

Starters are a set of convenient dependency descriptors that you can include in your application.
https://docs.spring.io/spring-boot/docs/2.1.8.RELEASE/reference/html/using-boot-build-systems.html#using-boot-starter

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<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
	<dependency>
		...       
    </dependency>
</dependencies>

Main procedure class,main entrance class

@SpringBootApplication

The @SpringBootApplication annotation is often placed on your main class, and it implicitly defines a base “search package” for certain items.

For example, if you are writing a JPA application, the package of the @SpringBootApplication annotated class is used to search for @Entity items.

Using a root package also allows component scan to apply only on your project.

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@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

below is the detail of @SpringBootApplication,which is like a gather.

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@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
), @Filter(
    type = FilterType.CUSTOM,
    classes = {AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication {

@SpringBootConfiguration

• @SpringBootConfiguration annotated class is an option class of Spring Boot.

@EnableAutoConfiguration

Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added.

You need to opt-in to auto-configuration by adding the @EnableAutoConfiguration or @SpringBootApplication annotations to one of your @Configuration classes.
(Because the @SpringBootConfiguration have included @EnableAutoConfiguration,the auto-configuration wil automatically configure all component that in the same package with the @SpringBootConfiguration)

Configuration file

Spring Boot default configuration in src/main/resources/.
application.yml or application.properties

1.YAML basic

format like Python
key:(space)value

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server:
	port: 8081
	path: /halo

do not ignore case

2. key: value

Object,Map

key: value

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friends:
	name:ring
	age:20
```  

inline	
``` yml
friends:{name:ring,age:20}

Array

-value

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pets:
	-cat
	-dog

inline

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pet: [dog,cat]

@ConfigurationProperties(prefix = “person”)

Bind all properties in this class with the properties in configuration file
prefix = "person" means bind class properties with person properties.

Only the component props can use the component function@ConfigurationProperties.

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@Component
@ConfigurationProperties
public class XXX{

@PropertySource(value = {“classpath:application2.yml’})

Like @ConfigurationProperties ,but this can select another configuration file.

@ImportResource

Import Spring configuration file,and
……..