Null Pointer Exception while using jdbcTemplate in Spring 3.0

Question

This is what I have tried so far.
DaoImpl.java

@Component
public class DaoImpl {
  @Autowired
  private DataSource dataSource;
  private JdbcTemplate jdbcTemplate;

  public DataSource getDataSource() {
    return dataSource;
  }

  public void setDataSource(DataSource dataSource) {
    this.jdbcTemplate = new JdbcTemplate(dataSource);
      }

  public JdbcTemplate getJdbcTemplate() {
    return jdbcTemplate;
  }

  public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
    this.jdbcTemplate = jdbcTemplate;
  }

  public int getCircleCount() {
    String sql = "select count(*) from circle";
    return (Integer)getJdbcTemplate().queryForObject(sql, Integer.class); //throws NPE
    //return getJdbcTemplate().queryForInt(sql);
  }
}

spring.xml

<bean id="dataSource"
    class="org.apache.commons.dbcp2.BasicDataSource">
    <property name="driverClassName" value="org.apache.derby.jdbc.ClientDriver" />
    <property name="url" value="jdbc:derby://localhost:1527/db" />
    <property name="initialSize" value="2"/>
    <property name="maxTotal" value="5"/>
</bean>

But I'm getting Null Pointer Exception at return statement of getCircleCount(). I'm learning Spring JDBC. Please help.

Answer 1

The problem is that the datasource gets injected directly into the field, but the setter is never called.

You need to move the @Autowired annotation from the field to the setter like so.

@Autowired
public void setDataSource(DataSource dataSource) {
    this.jdbcTemplate = new JdbcTemplate(dataSource);
}