java - Spring MVC - POJO 抛出无效 spring 的异常 :form information how to how to catch in controller

Question

我创建了 POJO，它验证产品名称不得少于 3 个字符。在 JSP 中使用 spring:form 在提交时创建对象。当我发送空白表单“名称”POJO 时抛出异常。 Controller 在 POST 方法中有 @Modelattribute 产品，但未创建产品对象，并且 APP 因 POJO 异常而崩溃。我想捕获此异常并将其作为错误消息添加回给用户。我做错了什么。

POJO代码:

public class Product {
private int id;
private String name;
private Department deparment;

public Product() {
}

// Create product from DB
public Product(int id, String name, Department deparment) {
    this.id = id;
    try {
        setName(name);
        setDeparment(deparment);
    } catch (ProductException | DeparmentException e) {
        e.getMessage();
        e.printStackTrace();
    }
}

// Create new product in DB
public Product(String name, Department deparment) {
    try {
        setName(name);
        setDeparment(deparment);
    } catch (ProductException | DeparmentException e) {
        e.getMessage();
        e.printStackTrace();
    }
}

public int getId() {
    return id;
}

public String getName() {
    return name;
}

public void setName(String name) throws ProductException {
    if (name.length() > 3) {
        this.name = name;
    } else {
        throw new ProductException("Invalid name for product");
    }
}

public Department getDeparment() {
    return deparment;
}

public void setDeparment(Department deparment) throws DeparmentException {
    if (deparment != null) {
        this.deparment = deparment;
    } else {
        throw new DeparmentException("Invalid deparment for product");
    }

}

JSP代码:

    <c:if test="${not empty error}">
    <p style="color: red">Error: ${error}</p>
</c:if>
<c:if test="${not empty success}">
    <p style="color: green">${success}</p>
</c:if>

<springForm:form action="product" method="post" commandName="product">

    <springForm:input type="text" placeholder="Име на продукта"
        path="name" pattern=".{3,}" />
    <br>
    <br>

    <select id="department" name="department">
        <option value="0">Department</option>
        <!-- Var mi e promenlivata items e masiva-->

        <c:forEach var="department" items="${departments}">
            <option value="${department.id}">${department.name}</option>
        </c:forEach>
    </select>
    <button>Create</button>
</springForm:form>

Controller 代码:

public class ProductController {

@RequestMapping(method = RequestMethod.GET, value = "/product")
public String showProductForm(Model viewModel) {
    DepartmentDAO deparmentDAO = new DepartmentDAO();
    List<Department> departments = new ArrayList<Department>();
    try {
        departments = deparmentDAO.selectAllDeparments();
    } catch (DeparmentException e) {
        e.printStackTrace();
    }
    viewModel.addAttribute("departments", departments);
    viewModel.addAttribute("product", new Product());

    return "product";
}

@RequestMapping(method = RequestMethod.POST, value = "/product")
public String addNewProduct(@ModelAttribute Product product, Model viewModel,@ModelAttribute("department") int departmentId, BindingResult result) {
    DepartmentDAO departmentDAO = new DepartmentDAO();
    ProductDAO productDAO = new ProductDAO();

    if (departmentId == 0) {
        viewModel.addAttribute("error", "Department is not selected.");
        return showProductForm(viewModel);
    }

    try {
        Department department = departmentDAO.getDepartmentById(departmentId);
        product.setDeparment(department);
        productDAO.addProduct(product);
    } catch (ProductException | DeparmentException e) {
        viewModel.addAttribute("error", e.getMessage());
        e.printStackTrace();
        return showProductForm(viewModel);
    }
    viewModel.addAttribute("success", "Въведохте успешно Продукта: <br>" + product.getName());

    return showProductForm(viewModel);
}

Answer 1

您不应该从 setter 中抛出异常；如果您这样做，Spring 将无法填充模型以将其传递给 Controller ​​。您应该为此使用验证；要么推出一个自定义的，这可能会引发您可以捕获的异常:

public void validate (Product p) throws ProductException() {...}

或者使用 Spring 的标准验证支持:

@RequestMapping(method = RequestMethod.POST, value = "/product")
public String addNewProduct(@ModelAttribute @Valid Product product, BindingResult result, Model viewModel,@ModelAttribute("department") int departmentId, BindingResult result) {...

请参阅 spring 文档以获取更多信息；我建议这个，这是标准方式