spring mvc 建立下拉框并进行验证demo

原文出处：http://howtodoinjava.com/spring/spring-mvc/spring-mvc-populate-and-validate-dropdown-example/

该例子主要介绍了如何对下拉框是否选值进行验证。其中验证主要使用JSR-303,数据绑定通过spring,该例子主要基于JSR-303验证例子的代码进行了简单的修改，其项目结构如下所示：

首先，添加DepartmentVO模型。

package com.howtodoinjava.demo.model;

public class DepartmentVO
{
    public DepartmentVO(Integer id, String name) {
        super();
        this.id = id;
        this.name = name;
    }

    private Integer id;
    private String name;

    public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

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

    @Override
    public String toString() {
        return "DepartmentVO [id=" + id + ", name=" + name + "]";
    }
}

　　然后在EmployeeVO类中添加DepartmentVO引用。

package com.howtodoinjava.demo.model;

import java.io.Serializable;

import javax.validation.constraints.NotNull;

import org.hibernate.validator.constraints.NotEmpty;

public class EmployeeVO implements Serializable
{
    private static final long serialVersionUID = 1L;

    private Integer id;

    @NotEmpty
    private String firstName;

    private String lastName;

    private String email;

    @NotNull
    private DepartmentVO department;

	//Setters and Getters
    public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}
	public DepartmentVO getDepartment() {
		return department;
	}

	public void setDepartment(DepartmentVO department) {
		this.department = department;
	}

    @Override
    public String toString() {
        return "EmployeeVO [id=" + id + ", firstName=" + firstName
                + ", lastName=" + lastName + ", email=" + email
                + ",department=" + department +"]";
    }
}

　　因为前台提交表单时，在post中department不是直接提交给后台一个实例，而是一个字符串，所以需要对其进行转换，在该例子中主要利用PropertyEditorSupport来对其进行转换。

package com.howtodoinjava.demo.convertor;

import java.beans.PropertyEditorSupport;
import com.howtodoinjava.demo.model.DepartmentVO;

public class DepartmentEditor extends PropertyEditorSupport
{
    //This will be called when user HTTP Post to server a field bound to DepartmentVO
    @Override
    public void setAsText(String id)
    {
        DepartmentVO d;
        switch(Integer.parseInt(id))
        {
            case 1: d = new DepartmentVO(1,  "Human Resource"); break;
            case 2: d = new DepartmentVO(2,  "Finance"); break;
            case 3: d = new DepartmentVO(3,  "Information Technology"); break;
            default: d = null;
        }
        this.setValue(d);
    }
}

　　这样当用户提交POST请求时，该方法就会被调用，并new一个对应的DepartmentVO实例。转换的目的实现了，然后就是让Spring使用这个类型，所以需要在EmployeeController中添加绑定方法。

package com.howtodoinjava.demo.controller;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.bind.support.SessionStatus;

import com.howtodoinjava.demo.convertor.DepartmentEditor;
import com.howtodoinjava.demo.model.DepartmentVO;
import com.howtodoinjava.demo.model.EmployeeVO;
import com.howtodoinjava.demo.service.EmployeeManager;

@Controller
@RequestMapping("/employee-module/addNew")
@SessionAttributes("employee")
public class EmployeeController {
    @Autowired
    EmployeeManager manager;

    private Validator validator;

    public EmployeeController()
    {
        ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
        validator = validatorFactory.getValidator();
    }
    @InitBinder
    public void initBinder(WebDataBinder binder) {
        binder.registerCustomEditor(DepartmentVO.class, new DepartmentEditor());
    }

    @ModelAttribute("allDepartments")
    public List<DepartmentVO> populateDepartments()
    {
        ArrayList<DepartmentVO> departments = new ArrayList<DepartmentVO>();
        departments.add(new DepartmentVO(-1,  "Select Department"));
        departments.add(new DepartmentVO(1,  "Human Resource"));
        departments.add(new DepartmentVO(2,  "Finance"));
        departments.add(new DepartmentVO(3,  "Information Technology"));
        return departments;
    }
    @RequestMapping(method = RequestMethod.GET)
    public String setupForm(Model model) {
        EmployeeVO employeeVO = new EmployeeVO();
        model.addAttribute("employee", employeeVO);
        return "addEmployee";
    }

    @RequestMapping(method = RequestMethod.POST)
    public String submitForm(@ModelAttribute("employee") EmployeeVO employeeVO,
            BindingResult result, SessionStatus status) {

        Set<ConstraintViolation<EmployeeVO>> violations = validator.validate(employeeVO);

        for (ConstraintViolation<EmployeeVO> violation : violations)
        {
            String propertyPath = violation.getPropertyPath().toString();
            String message = violation.getMessage();
            // Add JSR-303 errors to BindingResult
            // This allows Spring to display them in view via a FieldError
            result.addError(new FieldError("employee",propertyPath,

                                   "Invalid "+ propertyPath + "(" + message + ")"));
        }

        if (result.hasErrors()) {
            return "addEmployee";
        }
        // Store the employee information in database
        // manager.createNewRecord(employeeVO);

        // Mark Session Complete
        status.setComplete();
        return "redirect:addNew/success";
    }

    @RequestMapping(value = "/success", method = RequestMethod.GET)
    public String success(Model model) {
        return "addSuccess";
    }
}

　　然后是修改jsp文件。

<%@ page contentType="text/html;charset=UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>

<html>
<head>
    <title>Add Employee Form</title>
    <style>
    .error
    {
        color: #ff0000;
        font-weight: bold;
    }
    </style>
</head>

<body>
    <h2><spring:message code="lbl.page" text="Add New Employee" /></h2>
    <br/>
    <form:form method="post" modelAttribute="employee">
        <table>
            <tr>
                <td><spring:message code="lbl.firstName" text="First Name" /></td>
                <td><form:input path="firstName" /></td>
                <td><form:errors path="firstName" cssClass="error" /></td>
            </tr>
            <tr>
                <td><spring:message code="lbl.lastName" text="Last Name" /></td>
                <td><form:input path="lastName" /></td>
                <td><form:errors path="lastName" cssClass="error" /></td>
            </tr>
            <tr>
                <td><spring:message code="lbl.email" text="Email Id" /></td>
                <td><form:input path="email" /></td>
                <td><form:errors path="email" cssClass="error" /></td>
            </tr>

             <!-- DROPDOWN code -->

            <tr>
                <td><spring:message code="lbl.department" text="Department" /></td>
                <td><form:select path="department" items="${allDepartments}" itemValue="id" itemLabel="name" /></td>
                <td><form:errors path="department" cssClass="error" /></td>
            </tr>

            <tr>
                <td colspan="3"><input type="submit" value="Add Employee"/></td>
            </tr>
        </table>
    </form:form>
</body>
</html>

　　所有事情完成之后，发布到tomcat中，通过http://localhost:8080/dropdownDemo/employee-module/addNew访问。