如何从JSP页面保存JPA实体模型属性的特定属性

我们在jsp页面上使用JPA实体bean作为springmvc控制器的模型。我们的一个jsp页面是这个实体的局部视图,它没有显示所有属性。每当我们尝试从控制器使用服务层更新实体时,只有jsp表单上使用的属性被持久化,其他所有属性都被清空。处理这种情况的正确方法是什么?我们不希望必须在窗体上指定隐藏字段。

所以在这种情况下,当控制器调用服务.更新(client)方法名称字段将为空,因为在表单.jsp.

<form:form modelAttribute="client" method="get" action="${action}">
<table width="100%">
    <tr>
        <td>
            <table>
                <tr>
                    <td valign="top"><spring:message code="label.tradeOrderManagementSystem"/>:</td>
                    <td>
                        <form:select path="tradeOrderManagementSystems" >
                            <form:options items="${tradeOrderManagementSystemList}" itemValue="id" itemLabel="name" />
                        </form:select>
                        <a href="<spring:url value="/tradeOrderManagementSystem/add"/>" class="addAndReturn"><span><spring:message code="add"/></span></a>
                    </td>
                    <td>
                        <form:errors path="tradeOrderManagementSystems" cssClass="errors" />
                    </td>
                </tr>
                <tr><td></td><td>&nbsp;</td></tr>
            </table>
        </td>
    </tr>
</table>
<input type="hidden" name="submitted" value="true">

控制器

@RequestMapping("/{id}/edit")
public ModelAndView edit(HttpServletRequest request,
        HttpServletResponse response,
        @ModelAttribute("client") Client client,
        BindingResult result,
        @PathVariable("id") int id,
        Model model) {
    ControllerContext ctx = new ControllerContext(request, response);
    init(ctx);

    setAdvancedSearchAvailable(ctx, true);
    buildShowAndEditVerticalMenu(ctx, id, false);

    if (id == 0) {
        result.addError(new ObjectError("client", getMessage("error.idNeeded")));
        return getModelAndView(ctx, "itEfficiencies/form");
    } else {
        if (!isSubmission(ctx)) {
            client = clientService.find(id);
            model.addAttribute("client", client);
            fillClientForm(model);
            return getModelAndView(ctx, "itEfficiencies/form");
        } else {
            //clientValidator.validate(client, result);
            if (result.hasErrors()) {
                fillClientForm(model);
                return getModelAndView(ctx, "itEfficiencies/form");
            } else {
                try {
                    //checkClientProperties(client);
                    client.setId(id);
                    client = clientService.update(client);  //method updates only form fields and nulls out all others
                } catch (Exception e) {
                    e.printStackTrace();
                    result.addError(new ObjectError("client", getMessage("error.save")));
                    fillClientForm(model);
                    return getModelAndView(ctx, "itEfficiencies/form");
                }
                return getModelAndView(ctx, "/staffingByClient/" + client.getId() + "/show", true);
            }
        }
    }
}    

@Entity
public class Client extends AbstractEntity<Integer> {

private static final long serialVersionUID = 1L;

public static final String FIND_BY_NAME = "Client.FIND_BY_NAME";

public static final String COUNT_BY_NAME = "Client.COUNT_BY_NAME";

@Basic(optional = false)
@Column(nullable = false, length = 125)
private String name;

@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(inverseJoinColumns = {
    @JoinColumn(name = "trade_order_management_system_id")}, uniqueConstraints =
@UniqueConstraint(name = "UK_client_trade_order_mgmt_client_id_trade_order_mgmt_id",
columnNames = {"client_id", "trade_order_management_system_id"}))
@ForeignKey(name = "FK_client_trade_order_management_systems_client_id",
inverseName = "FK_client_trade_order_mgmt_sys_trade_order_management_system_id")
private List<TradeOrderManagementSystem> tradeOrderManagementSystems;

public Client() {
}

public Client(Integer id) {
    this.id = id;
}

public Client(Integer id, String name) {
    this.id = id;
    this.name = name;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}   

public List<TradeOrderManagementSystem> getTradeOrderManagementSystems() {
    return tradeOrderManagementSystems;
}

public void setTradeOrderManagementSystems(List<TradeOrderManagementSystem> tradeOrderManagementSystems) {
    this.tradeOrderManagementSystems = tradeOrderManagementSystems;
}

@Override
public boolean equals(Object object) {
    // TODO: Warning - this method won't work in the case the id fields are not set
    if (!(object instanceof Client)) {
        return false;
    }
    Client other = (Client) object;
    if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
        return false;
    }
    return true;
}

}

服务方式

public abstract class CrudService<T, ID extends Serializable> extends DAOImpl<T, ID> {

/**
 * Updates an entity from an existing entity.
 *
 * @since 0.0.1
 * 
 * @param entity
 * @return the managed instance of the updated entity
 */
@Override
@Transactional(rollbackFor = Exception.class, isolation = Isolation.READ_COMMITTED)
public T update(T entity, ID id) {
    return super.update(assignDefaultValues(entity), id);
}

public abstract class DAOImpl<T, ID extends Serializable> implements DAO<T, ID> {

private Class<T> persistentClass;

@PersistenceContext(unitName = "krfsPersistenceUnit")
protected EntityManager entityManager;

/**
 * Instantiates an instance of this class and sets the <code>persistentClass</code>
 * based on the identifier type
 *
 * @since 0.0.1
 */
public DAOImpl() {
    this.persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
}

/**
 * @since 0.0.1
 * 
 * @return the type to be persisted
 */
@Override
public Class<T> getPersistentClass() {
    return persistentClass;
}

/**
 * Updates an entity from an existing entity.
 *
 * @since 0.0.1
 * 
 * @param entity
 * @param id the identifier of the entity
 * 
 * @return the managed instance of the updated entity
 */
@Override
public T update(T entity, ID id) {
    //Find a managed instance of the entity first and copy the properties
    //to the passed in entity before merging.  This ensures that entityManager
    //will not create a new entity with merge.
    Object ref = this.entityManager.getReference(persistentClass, id);
    if (ref != null) {
        BeanUtils.copyProperties(entity, ref);
    }
    return (T) this.entityManager.merge(ref);
}

}