Spring Boot添加JDBC后启动失败：JdbcTemplate Bean未找到

错误日志 #

将启动ApplicationContext失败。若要显示条件评估报告，请启用'debug'模式重新运行应用。
2023-09-21T09:51:20.646+05:30 ERROR 18538 --- [ restartedMain] o.s.b.d.LoggingFailureAnalysisReporter :

---

应用启动失败 #

描述：
com.snigdha.snigdhahospitals.controller中的jdbcTemplate字段需要类型为'org.springframework.jdbc.core.JdbcTemplate'的Bean，但未找到。
注入点注解：

• @org.springframework.beans.factory.annotation.Autowired(required=true)

操作建议：
请在配置中定义类型为'org.springframework.jdbc.core.JdbcTemplate'的Bean。

问题场景 #

添加JDBC依赖后运行Spring Boot应用，启动失败，以下是项目的pom.xml和controller.java代码：

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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.snigdha</groupId>
    <artifactId>snigdhahospitals</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>snigdhahospitals</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>20</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-oauth2-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</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>
        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency> -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </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>

    <!-- <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                    <executions>
                            <execution>
                                <goals>
                                    <goal>repackage</goal>
                                </goals>
                            </execution>
                    </executions>
            </plugin>
        </plugins>
    </build> -->
</project>

controller.java #

package com.snigdha.snigdhahospitals;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.ModelAndView;

import com.snigdha.snigdhahospitals.model.Doctor;

@RestController
public class controller {

    @Autowired
    JdbcTemplate jdbcTemplate;

    @GetMapping("/d")
    public ResponseEntity<List<Doctor>> getDoctors(){
        List<Doctor> doctors = jdbcTemplate.query("SELECT * FROM DOCTOR", new BeanPropertyRowMapper<Doctor>(Doctor.class));
        return new ResponseEntity<>(doctors,HttpStatus.OK);
    }
    
    @RequestMapping("/")
    public ModelAndView home(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("home");
        return mv;
    }

    @RequestMapping("/home")
    public ModelAndView homepage(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("home");
        return mv;
    }

    @RequestMapping("/doctors")
    public ModelAndView doctors(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("doctors");
        return mv;
    }

    @RequestMapping("/login")
    public ModelAndView login(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("login");
        return mv;
    }

    @RequestMapping("/signup")
    public ModelAndView signup(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("signup");
        return mv;
    }

    @RequestMapping("/appointments")
    public ModelAndView appointments(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("appointments");
        return mv;
    }

    @RequestMapping("/contactus")
    public ModelAndView contactus(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("contactus");
        return mv;
    }

    @RequestMapping("/grievance")
    public ModelAndView grievance(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("grievance");
        return mv;
    }

    @RequestMapping("/aboutus")
    public ModelAndView aboutus(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("aboutus");
        return mv;
    }
    
}

解决方案 #

1. 添加数据库连接配置 #

Spring Boot的JdbcTemplate自动配置依赖有效的数据源配置，在src/main/resources/application.properties（或application.yml）中添加MySQL连接信息：

# 数据库连接配置
spring.datasource.url=jdbc:mysql://localhost:3306/你的数据库名?useSSL=false&serverTimezone=UTC
spring.datasource.username=你的数据库用户名
spring.datasource.password=你的数据库密码
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

2. 移除重复依赖 #

pom.xml中重复添加了spring-boot-starter-jdbc依赖，删除其中一处，保留一个即可：
删除以下重复的依赖块：

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

3. 手动配置JdbcTemplate（可选） #

如果上述步骤后仍无法自动创建JdbcTemplate Bean，可手动配置一个配置类生成Bean：

package com.snigdha.snigdhahospitals.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.core.JdbcTemplate;
import javax.sql.DataSource;

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

完成以上步骤后，重新启动应用即可解决JdbcTemplate Bean未找到的问题。

内容的提问来源于stack exchange，提问作者Vignesh