使用Spring Initializr创建Spring Boot项目

待我称王封你为后i 2023-06-27 08:41 9阅读 0赞

**目录**

一、创建项目

二、启动项目

三、创建web项目

--------------------

## 一、创建项目 ##

依次选择File -> New -> Project，设置好下图两点之后，点击next

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70][]

配置项目信息，点击next

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 1][]

配置Spring Boot版本及要引入的组件，这里我暂时不引入任何组件，点击next

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 2][]

最后配置项目名称、项目路径，点击finish

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 3][]

创建完的项目结构如下图所示，可以看到主要的文件夹是src，src/main/java里面是项目源代码，src/test/java里面是测试代码，两者包结构相对应，这个包结构就是创建项目时配置的com.example.demo。src/main/resources则是资源文件，IDEA自动帮我们创建了一个配置文件application.properties，我们以后创建的静态文件一般也是存放在这里。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 4][]

target目录如下所示：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 5][]

由于我们没有添加任何组件，pom文件如下所示

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.2.2.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>com.example</groupId>
        <artifactId>demo_01</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>demo</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    </project>

## 二、启动项目 ##

现在来启动项目，在启动之前，我们在Spring Boot项目的启动类中写上一句打印语句

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 6][]

点击运行，结果如下。可以看到程序的运行端口号是7408，打印语句输出了，程序以code 0码退出，此外还可以看到运行时间信息

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 7][]

## 三、创建web项目 ##

上面的项目马上就退出了，如果把它转变为web 项目，就可以持续运行。

首先，通过链接  [https://mvnrepository.com/search?q=SpringBoot+web][https_mvnrepository.com_search_q_SpringBoot_web]  查找并添加web依赖到pom文件

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzMwOTczNDMx_size_16_color_FFFFFF_t_70 8][]

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
                <version>2.2.2.RELEASE</version>
            </dependency>

创建com.example.demo.controller.HelloController

package com.example.demo.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    //注意，Spring Boot不能用Controller
    @RestController
    public class HelloController {
    
        @GetMapping("/hello")
        public String hello() {
            return "hello";
        }
    }

注意，就算在不同包下，也不能有同名的类。比如，创建com.springboot.controller.HelloController。则在启动项目时，会报以下错误。

2020-01-05 21:23:26.990  INFO 17712 --- [  restartedMain] com.example.demo.DemoApplication         : Starting DemoApplication on DESKTOP-CUG0QHK with PID 17712 (D:\WorkStations\Projects\SpringBoot\LoadToSpringBoot\demo\target\classes started by Think in D:\WorkStations\Projects\SpringBoot\LoadToSpringBoot\demo)
    2020-01-05 21:23:26.993  INFO 17712 --- [  restartedMain] com.example.demo.DemoApplication         : The following profiles are active: test
    2020-01-05 21:23:27.052  INFO 17712 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
    2020-01-05 21:23:27.052  INFO 17712 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
    2020-01-05 21:23:27.681  WARN 17712 --- [  restartedMain] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [com.example.demo.DemoApplication]; nested exception is org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name 'helloController' for bean class [com.springboot.controller.HelloController] conflicts with existing, non-compatible bean definition of same name and class [com.example.demo.controller.HelloController]
    2020-01-05 21:23:27.693 ERROR 17712 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed
    
    org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [com.example.demo.DemoApplication]; nested exception is org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name 'helloController' for bean class [com.springboot.controller.HelloController] conflicts with existing, non-compatible bean definition of same name and class [com.example.demo.controller.HelloController]
    	at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:184) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:325) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:242) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:275) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:95) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:706) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    	at com.example.demo.DemoApplication.main(DemoApplication.java:16) [classes/:na]
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]
    	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]
    	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]
    	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    Caused by: org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name 'helloController' for bean class [com.springboot.controller.HelloController] conflicts with existing, non-compatible bean definition of same name and class [com.example.demo.controller.HelloController]
    	at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.checkCandidate(ClassPathBeanDefinitionScanner.java:349) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.doScan(ClassPathBeanDefinitionScanner.java:287) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ComponentScanAnnotationParser.parse(ComponentScanAnnotationParser.java:132) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:290) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:245) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:202) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:170) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    	... 18 common frames omitted
    
    
    Process finished with exit code 0

另外，由于项目配置的包结构为com.example.demo，启动类就在这个包下面，我们编写的其他所有类也应该放在这个包下面。因为，Spring Boot是以启动类为起点，查找启动类所在的包以及其子包的所有类，并将其注入。如果在别的包下，像上面的com.springboot.controller包下的类在项目启动后就没有创建实例，自然就不能访问里面规定的URL。

当然，也可以指定要扫描的包来使得com.springboot.controller下的包得以注入，像下面的代码我们就通过ComponentScan注解指定扫描整个com包。

package com.example.demo;
    
    import com.example.demo.entity.BookConfigBean;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.context.properties.EnableConfigurationProperties;
    import org.springframework.context.annotation.ComponentScan;
    
    @SpringBootApplication
    //@ComponentScan(basePackages = {"com.demo.controller"})
    @ComponentScan(basePackages = {"com"})
    public class DemoApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(DemoApplication.class, args);
    
            System.out.println("打印日志...");
        }
    }

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[https_mvnrepository.com_search_q_SpringBoot_web]: https://mvnrepository.com/search?q=SpringBoot+web
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