Spring jdbcTemplate NPE exception

Question

I am trying to use the jdbcTemplate to query a MySQL database to get the SYSDATE. So the query is as simple as SELECT SYSDATE()

However, I get the following error:

Exception in thread "main" java.lang.NullPointerException
at com.trade.xml.modifier.Test.<init>(Test.java:18)
at com.trade.xml.modifier.TradeModifierApplication.main(TradeModifierApplication.java:17)

Here is a bit of what I do:

I created a DatabaseConfiguration.class which should take all the connection details from the application.properties

The application.properties looks like this:

spring.datasource.url=jdbc:mysql://localhost:3306/xmlconverter
spring.datasource.username=root
spring.datasource.password=
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MariaDBDialect

The DatabaseConfiguration.class looks like this

@Configuration
public class DatabaseConfiguration {

        @Value("${spring.datasource.driver-class-name}")
        private String driverName;

        @Value("${spring.datasource.url}")
        private String url;

        @Value("${spring.datasource.username}")
        private String userName;

        @Value("${spring.datasource.password}")
        private String password;

        @Bean(name = "dataSource")
        public DataSource dataSource() {
            final DriverManagerDataSource dataSource = new DriverManagerDataSource();
            dataSource.setDriverClassName(driverName);
            dataSource.setUrl(url);
            dataSource.setUsername(userName);
            dataSource.setPassword(password);
            return dataSource;
        }
    
    @Bean
    public JdbcTemplate dbjdbcTemplate() {
        return new JdbcTemplate(dataSource());
    }

}

2.I also created a Test.class where I wrote my method for querying

@Service
public class Test {
    
    //Since a bean is created in DatabaseConfiguration, 
    //"template = new JdbcTemplate()" is omitted (should be recognized automatically, right?)
    @Autowired
    private JdbcTemplate template;
    
    
    public String getDate() {
        String sql = "SELECT SYSDATE()";
        
        return template.queryForObject(sql, String.class);
    }

}

The main class looks as follows

 @SpringBootApplication
 public class TradeModifierApplication {

 public static void main(String[] args) {
     SpringApplication.run(TradeModifierApplication.class, args);

     Test test = new Test();
     System.out.println(test.getDate());

At this point I have read the whole Internet and I am not sure what is the root cause of this NPE. Any help/hints will be appreciated.

In your debugger is `template` wired?, as in it's not a null and spring constructed it — Chol Nhial, Dec 22 '20 at 23:47
Are those classes in different packages? If they are then you need to declare @ComponentScan with specific packages — devwebcl, Dec 22 '20 at 23:52
@CholNhial yes, so the problem comes when the return statement in Test is executed — Ne7WoRK, Dec 22 '20 at 23:55
@devwebcl Yes, everything is in the same package for now just so I understand how it works — Ne7WoRK, Dec 22 '20 at 23:55
@Ne7WoRK change your data type from String to LocalDateTime on `queryForObject` — Chol Nhial, Dec 23 '20 at 00:06
@CholNhial Yes, when I executed it from phpMyAdmin (since I am using XAMPP) it works as a charm from there — Ne7WoRK, Dec 23 '20 at 00:07
Sorry I deleted that comment it wasn't relevant. So try what I just said. There's a type mismatch. — Chol Nhial, Dec 23 '20 at 00:08
do you have `template.queryForObject(sql, LocalDateTime.class);` and you also need to change the return type — Chol Nhial, Dec 23 '20 at 00:11
@CholNhial Haha, I am not that newbie. Yes, I changed them both — Ne7WoRK, Dec 23 '20 at 00:12
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/226332/discussion-between-chol-nhial-and-ne7work). — Chol Nhial, Dec 23 '20 at 00:13

devwebcl · Answer 1 · 2020-12-23T00:58:13.617

0

The problem should be this line in TradeModifierApplication:

Test test = new Test();

You should let the spring container to instance Test class.

One way would be to inject by:

public static void main(String[] args) {
    ApplicationContext applicationContext = SpringApplication.run(TradeModifierApplication.class, args);
    Test service = applicationContext.getBean(Test.class);
    service.getDate());
}

}

edited Dec 23 '20 at 00:58

answered Dec 23 '20 at 00:20

devwebcl

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Maybe you are right, but then how to print the result of the query in the console ? – Ne7WoRK Dec 23 '20 at 00:28
https://stackoverflow.com/questions/49698963/how-to-call-a-service-from-main-application-calls-spring-boot – devwebcl Dec 23 '20 at 00:55
SomeService service = applicationContext.getBean(SomeService.class); service.doSth(args); – devwebcl Dec 23 '20 at 00:55
Still the same error.... – Ne7WoRK Dec 23 '20 at 01:23

Spring jdbcTemplate NPE exception

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