如何修复“加载应用程序上下文失败至少必须存在1个JPA元模型”

Question

我是springboot的新手，我正在尝试解决以下运行时错误：

java.lang.IllegalStateException: Failed to load ApplicationContext
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaAuditingHandler': Cannot resolve reference to bean 'jpaMappingContext' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: At least one JPA metamodel must be present!
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: At least one JPA metamodel must be present!
Caused by: java.lang.IllegalArgumentException: At least one JPA metamodel must be present!

如有任何帮助，我将不胜感激

这是我的POM：

<?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>2.1.2.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>io.rosesnconcrete.services</groupId>
<artifactId>sixersfacts</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>sixersfacts</name>
<description>restful service for sixers facts</description>

<properties>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.hibernate</groupId>
                <artifactId>hibernate-entitymanager</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.hibernate</groupId>
                <artifactId>hibernate-core</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.2.10.Final</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-security</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

spring.data.url = jdbc:mysql://localhost:3306/sixersfacts_app?useSSL=false
spring.datasource.username = root
spring.datasource.password = root
spring.datasource.testWhileIdle = true
spring.datasource.validationQuery = SELECT 1
spring.jpa.show-sql = true 
spring.jpa.properties.hibernate.dialect = 
org.hibernate.dialect.MYSQL5Dialect
spring.jpa.hibernate.ddl-auto = update
spring.autoconfigure.exclude = 
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration

package io.rosesnconcrete.services.model;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;
import javax.persistence.*;
import javax.validation.constraints.NotBlank;
import java.io.Serializable;
import java.util.Date;

@Entity
@Table(name = "facts")
@EntityListeners(AuditingEntityListener.class)
@JsonIgnoreProperties(value = {"createdAt", "updatedAt"}, allowGetters = 
true)
public class SixersFact implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@NotBlank
private String title;

@NotBlank
private String content;

@Column(nullable = false, updatable = false)
@Temporal(TemporalType.TIMESTAMP)
@CreatedDate
private Date createdAt;

@Column(nullable = false)
@Temporal(TemporalType.TIMESTAMP)
@LastModifiedDate
private Date updatedAt;

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public String getContent() {
    return content;
}

public void setContent(String content) {
    this.content = content;
}

public Date getCreatedAt() {
    return createdAt;
}

public void setCreatedAt(Date createdAt) {
    this.createdAt = createdAt;
}

public Date getUpdatedAt() {
    return updatedAt;
}

public void setUpdatedAt(Date updatedAt) {
    this.updatedAt = updatedAt;
}

@Override
public String toString() {
    return "SixersFact{" +
            "id=" + id +
            ", title='" + title + '\'' +
            ", content='" + content + '\'' +
            ", createdAt=" + createdAt +
            ", updatedAt=" + updatedAt +
            '}';
}

package io.rosesnconcrete.services.repository;

    import io.rosesnconcrete.services.model.SixersFact;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.stereotype.Repository;

@Repository
public interface SixersFactRepository extends 
JpaRepository<SixersFact,Long> {
}

package io.rosesnconcrete.services.sixersfacts;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.data.jpa.repository.config.EnableJpaAuditing;

@SpringBootApplication
@EnableJpaAuditing
public class SixersfactsApplication {

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

Answer 1

@springbootapplication只扫描当前（和子）包（参见1)，因此（Spring的）“组件扫描”不会拾取io.rosesnconcrete.services.model和io.rosesnconcrete.services.repository。并且类路径上有spring-boot-starter-data-jpa而没有@entityIE（在spring上下文中）会导致此错误消息。（见2）

一个“按设计”的快速解决方案：

将SixersFactsApplication移动到IO.RosesnConcrete.Services包（..或更高版本）。