Fail to connect to mysql when I using spring boot

Question

I want to make a web server with spring boot, but when I try to connect to my database, it comes some errors. Here are some parts of my code.

@Controller
public class BackgroundController {

private JdbcTemplate jdbcTemplate;
@RequestMapping("/RankingList")
@ResponseBody
public String RankingList(Model model){
    String sql="select userName,score from user;";
    List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
    try {
        list = jdbcTemplate.queryForList(sql);
    }catch (Exception e){
        return e.toString();
    }//return "RankingList";
}

}

Here are the dependencies in pom.xml;

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

Here are some parts of application.properties, where the 'em' is the name of my database;

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/em
spring.datasource.username=root
spring.datasource.password=qwerty
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

Here is the status of my database.

Connection id:          3
Current database:       em
Current user:           root@localhost
SSL:                    Not in use
Using delimiter:        ;
Server version:         5.7.18-log MySQL Community Server (GPL)
Protocol version:       10
Connection:             localhost via TCP/IP
Server characterset:    utf8
Db     characterset:    utf8
Client characterset:    utf8
Conn.  characterset:    utf8
TCP port:               3306

But when I get the url:http://localhost:4908/RankingList, the output is java.lang.NullPointerException.

I want to get help, and I will appreciate it very much.

Answer 1

You should add @Autowired to private JdbcTemplate jdbcTemplate;