如何在Spring MVC中使用多對多注釋將數據綁定到CheckBox

Question

我想這樣做；

我有一項工作可以改進CRUD應用程序，以學習Spring，Hibernate和JPA。 所以我想做很多對很多的例子，但是我請某人去做。

我想獲得員工的駕駛執照並更新信息。 我可以使用Spring forEach將員工的信息從數據庫中獲取到網頁中的CheckBox。 如果員工擁有哪個駕駛執照，則必須選中關系復選框。 我可以更新此信息。

例如，員工獲得了“ A1”和“ M”類的駕駛執照。 我可以獲取並綁定數據。

我創建了“員工”，“ driving_licenses”表。 我為商店員工的駕駛執照創建了“ employee_driving_licenses”表：

雇員：

id          int
last_name   nvarchar(20)
first_name  nvarchar(10)

駕駛執照：

id      int 
code    nvarchar(5)

employee_driving_licenses：

employee_id         int
driving_license_id  int

我創建了表的模型類，並添加了JPA批注。 我有Employee和DrivingLicense Entity Java類：

Employee.java

@Entity
@Table(name = "employees")
public class Employee {

    private int id;
    private String last_name;
    private String first_name;
    private java.util.Collection<DrivingLicense> driving_licenses = new HashSet<DrivingLicense>();

    @GeneratedValue(strategy = GenerationType.AUTO)
    @Id
    @Column
    public int getId() {
        return id;
    }

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

    @NotEmpty(message = "Please enter Last Name")
    @Column
    public String getLast_name() {
        return last_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    @NotEmpty(message = "Please enter First Name")
    @Column
    public String getFirst_name() {
        return first_name;
    }

    @ManyToMany(fetch = FetchType.EAGER, mappedBy = "employees")
    public java.util.Collection<DrivingLicense> getDriving_licenses() {
        return driving_licenses;
    }

    public void setDriving_licenses(
        java.util.Collection<DrivingLicense> driving_licenses) {this.driving_licenses = driving_licenses;
    }
}

DrivingLicense.java

@Entity
@Table(name = "driving_licenses")
public class DrivingLicense {

    private int id;
    private String code;
    private java.util.Collection<Employee> employees = new HashSet<Employee>();

    @Override
    public int hashCode() {
        return new Long(id).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
                return false;
        }
        if (!(obj instanceof DrivingLicense)) {
                return false;
        }
        return this.id == ((DrivingLicense) obj).getId();
    }

    @GeneratedValue(strategy = GenerationType.AUTO)
    @Id
    @Column
    public int getId() {
        return id;
    }

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

    @Column
    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    @ManyToMany(fetch = FetchType.EAGER, cascade = { CascadeType.PERSIST, CascadeType.MERGE })
    @JoinTable(name = "employee_driving_licenses", joinColumns = { @JoinColumn(name = "driving_license_id", nullable = false, updatable = false) }, inverseJoinColumns = { @JoinColumn(name = "employee_id", nullable = false, updatable = false) })
    public java.util.Collection<Employee> getEmployees() {
        return employees;
    }

    public void setEmployees(java.util.Collection<Employee> employees) {
        this.employees = employees;
    }
}

我創建了應用程序DAO，服務，控制器和視圖類/頁面。

EmployeeController.java：

@RequestMapping(value = "index", method = RequestMethod.POST)
public String employee(@Valid @ModelAttribute("employee") Employee employee,
    BindingResult result, @RequestParam String action,
    java.util.Map<String, Object> map) {

    boolean isValid = true;
    if (result.hasErrors()) {
        isValid = false;
    }

    Employee employeeResult = new Employee();
    switch (action.toLowerCase()) {
        case "add":
            if (isValid) 
                employeeService.add(employee);
            employeeResult = employee;
        break;

        case "edit":
            if (isValid) 
               employeeService.edit(employee);
            employeeResult = employee;
        break;
    }
    map.put("drivingLicenseList", drivingLicenseService.findActiveDrivingLicense());
    map.put("employee", employeeResult);
    map.put("activeEmployeeList", employeeService.findActiveEmployees());
    return "employee";
}

employee.jsp：

<c:forEach var="drive_licenses" items="${drivingLicenseList}">
    <form:checkbox path="driving_licenses"
    value="${drive_licenses }" label="${drive_licenses.code }" />
</c:forEach>

當我想更新員工的駕駛執照時，我收到如下錯誤代碼：

{employee=com.ay.model.Employee@573cb29c, org.springframework.validation.BindingResult.employee=org.springframework.validation.BeanPropertyBindingResult:     1 errors
Field error in object 'employee' on field 'driving_licenses': rejected value      [com.ay.model.DrivingLicense@1,com.ay.model.DrivingLicense@7,com.ay.model.DrivingLicense@8,com.ay.model.Driving    License@9]; codes     [typeMismatch.employee.driving_licenses,typeMismatch.driving_licenses,typeMismatch.java.util.Collection,typeMis    match]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes     [employee.driving_licenses,driving_licenses]; arguments []; default message [driving_licenses]]; default     message [Failed to convert property value of type 'java.lang.String[]' to required type 'java.util.Collection'     for property 'driving_licenses'; nested exception is java.lang.IllegalStateException: Cannot convert value of     type [java.lang.String] to required type [com.ay.model.DrivingLicense] for property 'driving_licenses[0]': no     matching editors or conversion strategy found]}

如何獲取Collection類型的值？ 請給我建議。

而且，如果我添加此代碼

value="${drive_licenses }" 

在employee.jsp的網頁上，我可以正常在瀏覽器上看到對象值。 其實首先我添加了這段代碼

value="${drive_licenses.id }"

但是沒有在CheckBoxes上檢查員工的駕駛執照，並且每個CheckBoxes值都為空。 真正的語法是什么？

感謝您的支持。

Answer 1

這個部分太多了。 大致：

一 ：創建包裝表格：

public class EmployeeForm{
    private Employee employee;

    //Driving licence needs a 'boolean' selected field
    //Mark as @Transient so not persisted
    //Otherwise create another wrapper/dto which has this boolean field
    //Spring MVC can only bind to indexed fields e.g. List
    private List<DrivingLicence> allAvailableLicences;

    public EmployeeForm(Employee employee, Collecion<DrivingLicence> licenes){
        //set instance vars
    }

    //getters
    //setters
}

二 ：將以下內容添加到您的控制器中：

//CALLED ON BOTH GET AND POST TO SET UP THE FORM
//FOR EDITING EXISTING EMPLOYEE REPLACE NEW EMPLOYEE WITH THE RELEVANT LOOKUP
@ModelAttribute("employeeForm")
public EmployeeForm getEmployeeForm(@RequestParam("employeeId", required = false) Long employeeId){
    return new EmployeeForm(new Employee(), drivingLicenseService.findActiveDrivingLicense());

}

三 ：

更改您的JSP表單以綁定到employeeForm：可以在路徑屬性中使用嵌套屬性，例如employee.name。 對於綁定許可證，您需要使用以下索引符號，即將列表中索引x處的許可證設置為選中。

<c:forEach var="licence" items="${employeeForm.allAvailableLicences}" varStatus="loop">
    <form:checkbox path="licence[${loop.index]}.selected" label="${licence.code }" />
</c:forEach>

四：

更新您的表單提交處理程序：

@RequestMapping(value = "index", method = RequestMethod.POST)
public String employee(@Valid @ModelAttribute("employeeForm") EmployeeForm employeeForm,
    BindingResult result, @RequestParam String action) {

    //validation etc

    Employee employee = employeeForm.getEmployee();

    for(DrivingLicence licence : employeeForm.getAllAvailableLicences()){
         //our indexed foem check box set the 'selected' field true
         //if selected add to the employee
    }

    //save updated employee

    return "nextPage";
}