spring boot介绍及使用详解

Spring Boot是由Pivotal团队提供的全新框架，其设计目的是用来简化新Spring应用的初始搭建以及开发过程。该框架使用了特定的方式来进行配置，从而使开发人员不再需要定义样板化的配置。通过这种方式，Boot致力于在蓬勃发展的快速应用开发领域（rapid application development）成为领导者。

Spring boot的特点

1. 创建独立的Spring应用程序
2. 嵌入的Tomcat，无需部署WAR文件
3. 简化Maven配置
4. 自动配置Spring
5. 提供生产就绪型功能，如指标，健康检查和外部配置
6. 绝对没有代码生成和对XML没有要求配置

Spring boot的优点

spring boot 可以支持你快速的开发出 restful 风格的微服务架构

自动化确实方便，做微服务再合适不过了，单一jar包部署和管理都非常方便。只要系统架构设计合理，大型项目也能用，加上nginx负载均衡，轻松实现横向扩展

spring boot 要解决的问题, 精简配置是一方面, 另外一方面是如何方便的让spring生态圈和其他工具链整合(比如redis, email, elasticsearch)

Spring boot的使用

1、maven配置文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
 
    <groupId>org.springboot.sample</groupId>
    <artifactId>spring-boot-sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>spring-boot-sample</name>
    <description>Spring Boot Sample Web Application</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.2.RELEASE</version>
        <relativePath /> 
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- MYSQL -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!-- Spring Boot JDBC -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

2、application类

@SpringBootApplication
@ServletComponentScan
public class SpringBootApplication extends SpringBootServletInitializer {
 
    private static final Logger logger = LoggerFactory.getLogger(SpringBootSampleApplication.class);
    public static void main(String[] args) {
        SpringApplication.run(SpringBootSampleApplication.class, args);
    }
}

3、配置类

@Repository
@Component
@Configuration
public class MyWebAppConfigurer extends WebMvcConfigurerAdapter implements EnvironmentAware{
    private static final Logger logger = LoggerFactory.getLogger(MyWebAppConfigurer.class);
    private RelaxedPropertyResolver propertyResolver;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 多个拦截器组成一个拦截器链
        // addPathPatterns 用于添加拦截规则
        // excludePathPatterns 用户排除拦截
        registry.addInterceptor(new MyInterceptor1()).addPathPatterns("/**");
        registry.addInterceptor(new MyInterceptor2()).addPathPatterns("/**");
        super.addInterceptors(registry);
    }
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/res/**").addResourceLocations("classpath:/res/");
        // 可以直接使用addResourceLocations 指定磁盘绝对路径，同样可以配置多个位置，注意路径写法需要加上file:
        registry.addResourceHandler("/imgs/**").addResourceLocations("file:D:/imgs/");
        super.addResourceHandlers(registry);
    }
}

4、添加filter

@WebFilter(filterName="myFilter",urlPatterns="/*")
public class MyFilter implements Filter {
    @Override
    public void destroy() {
        System.out.println("过滤器销毁");
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        System.out.println("执行过滤操作");    
        chain.doFilter(request, response);
    }
    @Override
    public void init(FilterConfig config) throws ServletException {
        System.out.println("过滤器初始化");
    }
}

5、controller

@RestController
@RequestMapping("/hello")
public class HelloController {
    @RequestMapping("/info")
    public Map<String, String> getInfo(@RequestParam String name) {
        Map<String, String> map = new HashMap<>();
        return map;
    }    
}

6、service

@Service
public class HelloWorldService {
    public String getHelloMessage() {
        return "Hello world";
    }
}

7、全局异常处理

@ControllerAdvice
 public class GlobalExceptionHandler {
     @ExceptionHandler(RuntimeException.class)
     @ResponseBody //在返回自定义相应类的情况下必须有，这是@ControllerAdvice注解的规定
     public MyExceptionResponse exceptionHandler(RuntimeException e, HttpServletResponse response) {
       
         return resp;
     }
 }
 说明：

@ControllerAdvice是controller的一个辅助类，最常用的就是作为全局异常处理的切面类
@ControllerAdvice可以指定扫描范围
@ControllerAdvice约定了几种可行的返回值，如果是直接返回model类的话，需要使用@ResponseBody进行json转换
1、返回String，表示跳到某个view
2、返回modelAndView
3、返回model + @ResponseBody

8、添加被其他配置使用的bean

@Bean
public PageHelper pageHelper(DataSource dataSource) {
    PageHelper pageHelper = new PageHelper();
    return pageHelper;
}

9、添加数据加载类

@Component
public class MyStartupRun implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println(">>>>>>>>>>>>>>>服务启动执行");
    }
}

该组件在项目启动时会立即执行
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