java - 休眠findall返回null

Question

我是 Java 新手，这是我在 Java 中的第一个项目。调用方法 findall() 时出现 NullPointerException。

我正在尝试从表中获取所有数据。

这是配置 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.springframework</groupId>
    <artifactId>gs-spring-boot-docker</artifactId>
    <version>0.1.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.1.RELEASE</version>
    </parent>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>${hibernate-core.version}</version>
            <scope>provided</scope>
        </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>

application.properties 配置我使用 postgres

server.port=8080
spring.datasource.platform=postgres
spring.datasource.url=jdbc:postgresql://postgres:5432/worlddb
spring.datasource.username=world_u
spring.datasource.password=world123
spring.datasource.testWhileIdle = true
spring.datasource.validationQuery = SELECT 1
spring.jpa.show-sql = true
spring.jpa.hibernate.ddl-auto=update
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.PostgreSQL9Dialect

我有实体国家和存储库

package hello.world.repository;

import java.lang.Exception;
import hello.world.entity.Country;
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
import javax.persistence.EntityManagerFactory;
import javax.persistence.*;
import org.springframework.stereotype.Repository;
import org.springframework.data.jpa.repository.*;
import java.util.*;

@Repository
public interface CountryRepository extends JpaRepository<Country, String> {
    List<Country> findAll();
}

我打电话给countryRepository.findAll(); 它返回空

标签： javahibernatespring-bootjpa