我尝试使用 Spring JPA 库来计算表中的行数，但我遇到了这个问题

Question

我是Spring Boot的初学者，在尝试学习时遇到了一个问题。尽管我努力解决它，但我找不到满意的解决方案。

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应用程序无法启动

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描述：

com.demo.QuizApp.service.QuestionService 中的字段 QuestionDAO 需要类型为“com.demo.QuizApp.dao.questionDAO”的 bean，但无法找到。

注入点有以下注释： - @org.springframework.beans.factory.annotation.Autowired（必需= true）

行动：

考虑在配置中定义“com.demo.QuizApp.dao.questionDAO”类型的 bean。**

这是我的代码。 QuestionContoller.java

package com.demo.QuizApp.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.demo.QuizApp.service.QuestionService;

@RestController
@RequestMapping("questions")
public class QuestionContoller {

    @Autowired
    QuestionService questionService;

    @GetMapping("AllQuestions")
    public Long getAllQuestionAll() {
        return questionService.getAllQuestionAll();
    }
}

问题服务.java

package com.demo.QuizApp.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.demo.QuizApp.dao.questionDAO;

@Service
public class QuestionService {

    @Autowired
    questionDAO questionDAO;

    public long getAllQuestionAll() {
        return questionDAO.count();
    }
}

问题.java

package com.demo.QuizApp.model;

import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
import lombok.Data;

@Data
@Entity
@Table(name = "Question")
public class Question {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private int id;
    @Column(name = "questionTitle")
    private String questionTitle;
    @Column(name = "rightAnswer")
    private String rightAnswer;
    @Column(name = "diffcultyLevel")
    private String diffcultyLevel;
    @Column(name = "option1")
    private String option1;
    @Column(name = "option2")
    private String option2;
    @Column(name = "option3")
    private String option3;
    @Column(name = "option4")
    private String option4;
    
    
}

QuestionDAO.java

package com.demo.QuizApp.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.demo.QuizApp.model.Question;

@Repository
public interface questionDAO  extends JpaRepository<Question, Integer>{

}

应用程序.pro

spring.application.name=QuizApp
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://localhost:5432/QuestionDB
spring.datasource.username=postgres
spring.datasource.password=root
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect
spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration 

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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.3</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    
    <groupId>com.demo</groupId>
    <artifactId>QuizApp</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>QuizApp</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>


        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>4.1.4.Final</version>
        </dependency>
        
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.2.3.Final</version>
        </dependency>
        <dependency>
            <groupId>javax.xml.bind</groupId>
            <artifactId>jaxb-api</artifactId>
            <version>2.3.0</version>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

我想使用JPA的默认方法。

Answer 1

欢迎使用 Spring Boot！

尝试从 application.properties 中删除

spring.autoconfigure.exclude

行。

DataSourceAutoConfiguration

是SpringBoot的众多自动配置类之一。它负责在启动时实例化 JPA 存储库 bean，但您不小心禁用了它。