title: I can't use findOne() method in my code
body: <p>I have error in my app, because I use findOne() method. Below my simple code. In User class my id is String email and that's id I'm trying to use in my class UserService like this :  </p>
  
  <pre><code>public User findUser(String email){
      return userRepository.findOne(email);
  }
  </code></pre>
  
  <p>but I have this error:</p>
  
  <blockquote>
    <p>method findOne in interface org.springframework.data.repository.query.QueryByExampleExecutor cannot be applied to given types;<br>
      required: org.springframework.data.domain.Example<br>
      found: java.lang.String<br>
      reason: cannot infer type-variable(s) S
        (argument mismatch; java.lang.String cannot be converted to org.springframework.data.domain.Example)</p>
  </blockquote>
  
  <p>User class:</p>
  
  <pre><code>@Entity
  @Data
  @Table(name = "User")
  public class User {
      @Id
      @Email
      @NotEmpty
      @Column(unique = true)
      private String email;
  
      @NotEmpty
      private String name;
  
      @NotEmpty
      @Size(min = 5)
      private String password;
  
      @OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
      private List&lt;Task&gt; tasks;
  
      @ManyToMany(cascade = CascadeType.ALL)
      @JoinTable(name = "USER_ROLE", joinColumns = {
          @JoinColumn(name = "USER_EMAIL", referencedColumnName = "email")
      }, inverseJoinColumns = {@JoinColumn(name = "ROLE_NAME", referencedColumnName = "name")})
      private List&lt;Role&gt; roles;
  }
  </code></pre>
  
  <p>and UserRepository:</p>
  
  <pre><code>public interface UserRepository extends JpaRepository&lt;User, String&gt; {
  }
  </code></pre>