springboot2.2.6.RELEASE chapter3

Spring Boot favors Java-based configuration. Although it is possible to use SpringApplication with
XML sources, we generally recommend that your primary source be a single @Configuration class.
Usually the class that defines the main method is a good candidate as the primary @Configuration.

example:

1. Configuration Classes （ 使用java类进行配置 ）

package com.github;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class TestConfig {

    @Bean
    public TestBean testBean() {
        TestBean testBean = new TestBean();
        testBean.setConfig1("testBean config");
        return testBean;
    }
}

这个配置就等同于之前在xml里的配置

<beans>
    <bean id="testBean" class="com.github.TestBean"/>
</beans>

2. Auto-configuration （ 自动配置 ）

Spring Boot自动配置尝试根据您添加的jar依赖项自动配置Spring应用程序。例如，如果HSQLDB在您的类路径上，并且您没有手动配置任何数据库连接bean，那么Spring Boot将自动配置内存中的数据库。

3. Disabling Specific Auto-configuration Classes （ 取消自动配置 ）

package com.github.examples;


import com.github.TestConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.Import;
import org.springframework.web.bind.annotation.RestController;

//@SpringBootApplication()
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
@RestController
@Import({TestConfig.class})
@ServletComponentScan
public class DemoApplication {

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

}