在课堂上找不到Social_Security_Number的setter / field

Question

我收到此警告，然后是后续的NullpointerException。

在仔细阅读了一些文章后，我尝试确保我的Java类名称与我的Firebase数据库中的名称相匹配，但我仍然遇到错误。

FirebaseDB：

警告/错误：

01-03 13:03:01.963 23252-23252/? I/FirebaseMethods: checkIfUsernameExists: checking if [email protected] already exists.
01-03 13:03:01.965 23252-23252/? I/FirebaseMethods: checkIfUsernameExists: datasnapshot: DataSnapshot { key = RC9zIioE6vc5vlhrIethmbqyFDS2, value = {Social_Security_Number=5555, [email protected]} }
01-03 13:03:01.981 23252-23252/? W/ClassMapper: No setter/field for Social_Security_Number found on class com.netgalaxystudios.timeclock.Models.EmployeeUser
01-03 13:03:01.981 23252-23252/? W/ClassMapper: No setter/field for Email_Address found on class com.netgalaxystudios.timeclock.Models.EmployeeUser
01-03 13:03:01.981 23252-23252/? I/FirebaseMethods: checkIfUsernameExists: email: null
01-03 13:03:01.987 23252-23252/? E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
                                                          at com.netgalaxystudios.timeclock.Adapters.FirebaseMethods.checkIfUsernameExists(FirebaseMethods.java:46)
                                                          at com.netgalaxystudios.timeclock.Activities.RegisterEmployeeActivity$1$1.onDataChange(RegisterEmployeeActivity.java:122)

firebase methods.Java:

public boolean checkIfUsernameExists(String emailAddress, DataSnapshot datasnapshot){
        Log.i(TAG, "checkIfUsernameExists: checking if " + emailAddress + " already exists.");

        EmployeeUser user = new EmployeeUser();

        for (DataSnapshot ds: datasnapshot.getChildren()){
            Log.i(TAG, "checkIfUsernameExists: datasnapshot: " + ds);

            user.setEmailAddress(ds.getValue(EmployeeUser.class).getEmailAddress());
            Log.i(TAG, "checkIfUsernameExists: email: " + user.getEmailAddress());

            if(user.getEmailAddress().equals(emailAddress)){
                Log.i(TAG, "checkIfUsernameExists: FOUND A MATCH: " + user.getEmailAddress());
                return true;
            }

employee user.Java:

public class EmployeeUser {

    private String user_id;
    private String Email_Address;
    private String Social_Security_Number;

    public EmployeeUser(String user_id, String Email_Address, String Social_Security_Number) {
        this.user_id = user_id;
        this.Email_Address = Email_Address;
        this.Social_Security_Number = Social_Security_Number;
    }

    public EmployeeUser(String Email_Address) {
        this.Email_Address = Email_Address;
    }

    public EmployeeUser() {}

    public String getUser_id() {
        return user_id;
    }

    public void setUser_id(String user_id) {
        this.user_id = user_id;
    }

    public String getEmailAddress() {
        return Email_Address;
    }

    public void setEmailAddress(String emailAddress) {
        this.Email_Address = emailAddress;
    }

    public String getSocialSecurityNumber() {
        return Social_Security_Number;
    }

    public void setSocialSecurityNumber(String socialSecurityNumber) {
        this.Social_Security_Number = socialSecurityNumber;
    }

}

register employee activity.Java:

 mDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
                            @Override
                            public void onDataChange(DataSnapshot dataSnapshot) {
                                //1st check: Make sure the username is not already in use
                                Log.i("DATA VALUE", dataSnapshot.child("RC9zIioE6vc5vlhrIethmbqyFDS2").getValue().toString());

                                if (firebaseMethods.checkIfUsernameExists(email, dataSnapshot)) {
                                    auth.createUserWithEmailAndPassword(emailET.getText().toString(), passwordET.getText().toString())
                                            .addOnCompleteListener(RegisterEmployeeActivity.this, new OnCompleteListener() {

Answer 1

根据Java Naming conventions，您的模型类应如下所示：

public class EmployeeUser {
    private String userId;
    private String emailAddress;
    private String socialSecurityNumber;

    public EmployeeUser(String userId, String emailAddress, String socialSecurityNumber) {
        this.userId = userId;
        this.emailAddress = emailAddress;
        this.socialSecurityNumber = socialSecurityNumber;
    }

    public EmployeeUser(String emailAddress) {
        this.emailAddress = emailAddress;
    }

    public EmployeeUser() {}

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getEmailAddress() {
        return emailAddress;
    }

    public void setEmailAddress(String emailAddress) {
        this.emailAddress = emailAddress;
    }

    public String getSocialSecurityNumber() {
        return socialSecurityNumber;
    }

    public void setSocialSecurityNumber(String socialSecurityNumber) {
        this.socialSecurityNumber = socialSecurityNumber;
    }
}

你得到No setter/field for Social_Security_Number found on class错误，因为Firebase正在根据你的socialSecurityNumber getter方法寻找一个名为getSocialSecurityNumber()的字段。你的字段是Social_Security_Number而不是socialSecurityNumber因此错误。