初学spring boot踩过的坑

一、搭建spring boot环境

　　maven工程

　　　　　　pom文件内容

<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>com.qm.demo</groupId>
<artifactId>springbootDemo</artifactId>
<version>0.0.1-SNAPSHOT</version>

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.2.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
   <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
   <dependency>
       <groupId>MySQL</groupId>
       <artifactId>mysql-connector-Java</artifactId>
       <version>5.0.8</version>
   </dependency>
   <dependency>
       <groupId>com.alibaba</groupId>
       <artifactId>druid</artifactId>
       <version>1.0.9</version>
   </dependency>
   <dependency>
    <groupId>org.antlr</groupId>
    <artifactId>antlr4-runtime</artifactId>
    <version>4.1</version>
</dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <scope>provided</scope>
</dependency>
</dependencies>

</project>

项目目录结构

　　其中springTest类是spring boot内部tomcat启动时要运行的类

其中内容如下

package com.qm;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

import com.qm.controller.UserController;

@SpringBootApplication
public class SpringTest {

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

Application类的作用是外部服务器启动spring boot所要做的一些事。内容如下

package com.qm;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.support.SpringBootServletInitializer;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan
public class Application extends SpringBootServletInitializer{
   /**
     * 实现SpringBootServletInitializer可以让spring-boot项目在web容器中运行
     */
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        builder.sources(this.getClass());
        return super.configure(builder);
    }

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

    }
}

application.properties文件内容如下

server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3309/springbootdemo
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
spring.devtools.livereload.enabled=true

//热部署，需要提供的路径
spring.devtools.restart.additional-paths=src\main\java\com\qm
spring.thymeleaf.cache=false

踩过的坑

坑一，

一开始以为文件目录，可以随便放，经过坑一的教训，才知道代码文件存放有一定的顺序

如上项目结构图，其中springtest类和application类一定要放在最外面的包里，如com.qm 当启动spring boot时，它会去加载com.qm包及其子包下的所有类，

当你不按顺序时，且代码中有@Autowired注解注入bean时，会报以下错误

Description:

Field userService in com.qm.controller.UserController required a bean of type 'com.qm.service.UserService' that could not be found.

Action:

Consider defining a bean of type 'com.qm.service.UserService' in your configuration.
,即bean找不到。，这是应该注意代码顺序。

坑二

补齐坑一后，在service层的接口继承jpa，然后在controller层使用注入的service方法会报以下错误

Error creating bean with name 'dataController': Unsatisfied dependency expressed through field 'personRepository'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personRepository': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property auto found for type Person!

这是因为hibernate版本的问题，

只要加上

<dependency>
    <groupId>org.antlr</groupId>
    <artifactId>antlr4-runtime</artifactId>
    <version>4.1</version>

这个依赖即可

添加之后，若maven仓库中有该jar包，最好删掉，编译时重新下载

若spring boot正常启动，而地址栏访问不到controller,则此时应该注意，spring boot启动时，未扫描到controller类，

在spring boot入口类上再添加一个注解

@ComponentScan("要扫描的包名")

以上就是我在学spring boot时遇到过得一些坑。