Explication about Spring Converter with Spring MVC - I can't understand - spring

Question

I'd like someone could explication about converter in spring mvc.
My domain class:
#Entity
#Table(name = "TIME_SHEET")
public class TimeSheet implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "ID_TIME_SHEET")
private Long id;
#NotNull(message = "timesheet.cadastro.horainicio.obrigatorio")
#Temporal(TemporalType.TIME)
#Column(name = "INICIO", nullable = false)
private Date horaInicio;
#NotNull(message = "timesheet.cadastro.horafim.obrigatorio")
#Temporal(TemporalType.TIME)
#Column(name = "FIM", nullable = false)
private Date horaFim;
#Column(name = "LATITUDE", nullable = true)
private Double latitude;
#Column(name = "LONGITUDE", nullable = true)
private Double longitude;
#Size(max = 300,message = "timesheet.cadastro.observacao.acimaDoPermitido")
#Column(name = "OBSERVACAO", nullable = true)
private String observacao;
//#NotNull(message = "timesheet.cadastro.dia.obrigatorio")
#ManyToOne(cascade = javax.persistence.CascadeType.ALL)
#JoinColumn(name = "ID_DIAS")
private Dias dia;
//#NotNull(message = "timesheet.cadastro.usuario.obrigatorio")
#ManyToOne(cascade = javax.persistence.CascadeType.ALL)
#JoinColumn(name = "ID_USUARIO")
private Usuario usuario;
...
My class converter:
public class IdToUsuarioConverter implements Converter<String, Usuario> {
#Autowired
private IusuarioService usuarioService;
public Usuario convert(String id) {
return usuarioService.buscaPorId(Long.valueOf(id));
}
}
In my springmvc.xml:
<mvc:annotation-driven conversion-service="conversionService"/>
<bean id="conversionService"
class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<set>
<bean class="br.com.infowhere.timeSheet.converter.IdToUsuarioConverter"/>
</set>
</property>
</bean>
I don't have problem, but my question is:
1-) When my converter will act ?
2-) My .jsp will post a form where I have one list similar:
<form:select path="user" items="${userList}" multiple="false" />
HTML:
<select id="user" name="user">
<option value="1">User 1</option>
<option value="2">User 2</option>
</select>
At what time my converter will work ?
I'm sorry but I'm trying to understand about converter.
thanks !!!

Answer 1

Your converter will convert id's to Usario objects in your controllers.
For example:
#Controller
public class MyController {
#RequestMapping("/showUsario")
public String showUsario(#RequestParam("id") Usario usario, Model model) {
model.addAttribute("usario", usario);
return "showUsario";
}
}
Then a request to /showUsario?id=123 will convert String "123" to Usario using the converter. If you didn't have a converter you would have to put String id (instead of Usario) in method parameters and manually convert the id to Usario. This way, Spring does it for you using your converter.