java - 字段 jdbcTemplate 需要类型为 'org.springframework.jdbc.core.JdbcTemplate' 的 bean，但无法找到

Question

我做了这个简单的应用程序来连接到 MySQL 数据库，我收到了这个错误:

org.springframework.jdbc.core.JdbcTemplate

在我的配置中 (com.kubamadry.dao.MySqlStudentDao) :

*****************************
APPLICATION FAILED TO START
*****************************

Description:

Field jdbcTemplate in com.kubamadry.dao.MySqlStudentDao required a bean of type 'org.springframework.jdbc.core.JdbcTemplate' that could not be found.


Action:

Consider defining a bean of type 'org.springframework.jdbc.core.JdbcTemplate' in your configuration.

Disconnected from the target VM, address: '127.0.0.1:49838', transport: 'socket'

Process finished with exit code 1

项目结构:

Image

类(class)

主页

package com.kubamadry;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

学生

package com.kubamadry.entity;

public class Student {
    private int id;
    private String name;
    private String course;
}
//Constructor, getters and setters

学生 Controller

package com.kubamadry.controller;

import com.kubamadry.entity.Student;
import com.kubamadry.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.*;

import java.util.Collection;

@RestController
@RequestMapping("/students")
public class StudentController {

    @Autowired
    private StudentService studentService;

    @RequestMapping(method = RequestMethod.GET)
    public Collection<Student> getAllStudents() {
        return studentService.getAllStudents();
    }

    @RequestMapping(value = "/{id}", method = RequestMethod.GET)
    public Student getStudentById(@PathVariable int id) {
        return studentService.getStudentById(id);
    }

    @RequestMapping(value = "/{id}", method = RequestMethod.DELETE)
    public void deleteStudentById(@PathVariable int id) {
        studentService.deleteStudentById(id);
    }

    @RequestMapping(method = RequestMethod.PUT, consumes = MediaType.APPLICATION_JSON_VALUE)
    public void updateStudent(@RequestBody Student student) {
        studentService.updateStudent(student);
    }

    @RequestMapping(method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
    public void addStudent(@RequestBody Student student) {
        studentService.addStudent(student);
    }
}

MySqlStudentDao

package com.kubamadry.dao;

import com.kubamadry.entity.Student;
import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;
import org.springframework.jdbc.core.JdbcTemplate;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Collection;
import java.util.List;

@Repository("mysql")
public class MySqlStudentDao implements StudentDao {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public Collection<Student> getAllStudents() {
        final String sql = "SELECT * FROM students";
        List<Student> students = jdbcTemplate.query(sql, new RowMapper<Student>() {
            @Override
            public Student mapRow(ResultSet resultSet, int i) throws SQLException {
                Student student = new Student();
                student.setId(resultSet.getInt("id"));
                student.setName(resultSet.getString("name"));
                student.setCourse(resultSet.getString("course"));
                return student;
            }
        });
        return students;
    }

    @Override
    public Student getStudentById(int id) {
        return null;
    }

    @Override
    public void deleteStudentById(int id) {
         //
    }

    @Override
    public void updateStudent(Student student) {
         //
    }

    @Override
    public void addStudent(Student student) {
         //
    }
}

应用程序属性

spring.datasource.url=jdbc:mysql://localhost/students
spring.datasource.username=root
spring.datasource.password=password123

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>

    <groupId>com.kubamadry</groupId>
    <artifactId>workingProject</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
    </parent>

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

        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.5</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.3.4.RELEASE</version>
        </dependency>

    </dependencies>

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


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

</project>

请帮我解决这个问题。

Answer 1

您需要申报JdbcTemplate bean 中任意@Configuration类，例如:

@Bean
public JdbcTemplate jdbcTemplate(DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}

另外，考虑使用 spring-boot-starter-jdbc而不是 spring-jdbc依赖。入门模块包含您将来需要的大部分库。

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>