未能实例化类 HeroController；构造函数抛出异常
我正在为我的网络应用程序使用 SpringBoot，但遇到以下错误：
上下文初始化期间遇到异常 - 取消刷新尝试：org.springframework.beans.factory.BeanCreationException：创建名称为“heroController”的 bean 在文件 [D:\Projects\Java\mydbexxcercise\target\classes\com\db\controllers 中定义时出错\HeroController.class]: bean实例化失败；嵌套异常是 org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.db.controllers.HeroController]: Constructor throw exception; 嵌套异常是 java.lang.NullPointerException。
这些是我的课程：
DBApp 类（主类）：
package com.db.app;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
/*
* DAL - Data Access Layer
* BL - Business Layer
*
* */
@SpringBootApplication
@ComponentScan(basePackages = {"com.db.controllers","com.db.services"})
@EnableJpaRepositories(basePackages = "com.db.repositories")
@EntityScan(basePackages = "com.db.entities")
public class DBApp
{
public enum PowerCatagory{SpecialPower,Weapon,Machines}
private static ConfigurableApplicationContext appContext;
public static void main(String[] args)
{
appContext = SpringApplication.run(DBApp.class,args);
}
public static ConfigurableApplicationContext getAppContext()
{
return appContext;
}
}
英雄库类：
@Repository
public interface HeroRepository extends JpaRepository<Hero, Integer>
{
}
根据控制台，Spring无法初始化HeroController的原因是以下代码导致的异常：
private HeroService heroService = DBApp.getAppContext().getBean(HeroService.class);
我不知道为什么会在此处抛出异常，因此非常感谢您的帮助。非常感谢您的宝贵时间
翻过高山走不出你2回答
-
慕神8447489
将您的移动DBApp到com.db包。删除所有注释，但@SpringBootApplication其他注释是隐含的和自动检测的删除getAppContext方法。这样你的DBApp班级应该看起来像这样。package com.db;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class DBApp { public enum PowerCatagory{SpecialPower,Weapon,Machines} public static void main(String[] args) { SpringApplication.run(DBApp.class,args); }}现在在你HeroService和HeroController你需要使用依赖注入。最佳实践是使用构造函数注入而不是字段注入。@Servicepublic class HeroService { private final HeroRepository heroRepository; public HeroService(HeroRepository heroRepository) { this.heroRepository=heroRepository; }这HeroController@RestControllerpublic class HeroController { private final HeroService heroService; public HeroController(HeroService heroService) { this.heroService=heroService; }注意：上的@Repository注释HeroRepository可以删除，因为它没有添加任何内容。接下来你的依赖有点乱，使用专用的 spring-boot-starters 来获得正确的和经过测试的版本。您不需要 Hibernate/JPA 依赖项（它们包含在 中spring-boot-starter-data-jpa），其他人需要较新的版本。<?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>MyDBExcercise</groupId> <artifactId>mydbexxcercise</artifactId> <version>1.0-SNAPSHOT</version> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-parent</artifactId> <version>2.1.4.RELEASE</version> </parent> <dependencies> <dependency> <groupId>com.aerospike</groupId> <artifactId>spring-data-aerospike</artifactId> <version>2.0.1.RELEASE</version> </dependency> <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>org.postgresql</groupId> <artifactId>postgresql</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build></project> -
慕容森
以下 2 个更改应该可以解决此问题。无需从 App Context 获取 bean。@Servicepublic class HeroService { @Autowired private HeroRepository heroRepository;&@RestControllerpublic class HeroController { @Autowired private HeroService heroService;& pom.xml<?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><parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.4.RELEASE</version> <relativePath/> <!-- lookup parent from repository --></parent><groupId>MyDBExcercise</groupId><artifactId>mydbexxcercise</artifactId><version>0.0.1-SNAPSHOT</version><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> </dependency> <dependency> <groupId>com.aerospike</groupId> <artifactId>spring-data-aerospike</artifactId> <version>1.0.2.RELEASE</version> </dependency> <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>org.postgresql</groupId> <artifactId>postgresql</artifactId> </dependency></dependencies><build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins></build>& application.propertiesspring.datasource.url=jdbc:postgresql://localhost:5432/postgresspring.datasource.username=postgresspring.datasource.password=*****spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true
随时随地看视频慕课网APP
相关分类
Java