Convert DTO to List of parameter

Question

public class CreateCustomerRequest {
    private String fName;
    private String lName;
    private String gender;
    private String address1;
    private String address2;
    private String mobileNo;
}

I have above Request DTO. What I need when I will get this request then I need to convert this DTO with List<String> fields; Where List<String> objects contains {fName, lName, gender, address1, address2, mobileNo}

Please suggest how I will achieve this. Not getting any idea.

Do you mean that u need to convert the attributes of this DTO to a list? — sana, Aug 30 '18 at 05:34
Right, so do you just mean `Arrays.asList(fName, lName, gender, ...)`? — Phil, Aug 30 '18 at 05:38
@Shiladittya Reflection API is useful to get declared field of DTO class — Snehal Patel, Aug 30 '18 at 05:38
Possible duplicate of [Printing all variables value from a class](https://stackoverflow.com/questions/1526826/printing-all-variables-value-from-a-class) — Phil, Aug 30 '18 at 05:42

Mehdi Tahmasebi · Accepted Answer · 2018-09-01T04:43:54.097

Based on reflection, if you make fields public the below code work, if you want to make them private instead of setting field you can convert it by constructor.

public class CreateCustomerRequest {
    public String fName;
    public String lName;
    public String gender;
    public String address1;
    public String address2;
    public String mobileNo;
}


public static void main(String[] args) throws Throwable {
    List<String> param = new ArrayList<String>();
    param.add("fnameValue");
    param.add("lNameValue");
    param.add("genderValue");
    param.add("address1Value");
    param.add("address2Value");
    param.add("mobileNoValue");
    CreateCustomerRequest object = convert(param, CreateCustomerRequest.class);
    System.out.println("Gender : " + object.gender);
}

public static <T extends Object> T convert(List<String> param, Class<T> clazz) throws Throwable
{
    Constructor<?> ctor = clazz.getConstructor();
    T result = (T) ctor.newInstance();
    Field[] fields = result.getClass().getFields();
    if(fields == null)
        return null;
    for(int i =0;i<fields.length;i++)
    {
        if(fields[i].getType().equals(String.class))
        {
            if(param.size() > i)
                fields[i].set(result, param.get(i));
        }
    }       
    return result;
}

Cheers.

EDIT

For making DTO class fields private and read them via getter method, I edited my answer to support it.

Changes :

Convert result.getClass().getFields() ---> result.getClass().getDeclaredFields() to able read privatye fields.
calling fields[i].setAccessible(true) before setting value to field.
Read field value via getter --> System.out.println("Gender : " + object.getGender());

so new code of DTO class is :

public class CreateCustomerRequest {
    private String fName;
    private String lName;
    private String gender;
    private String address1;
    private String address2;
    private String mobileNo;

    public String getfName() {
        return fName;
    }
    public void setfName(String fName) {
        this.fName = fName;
    }
    public String getlName() {
        return lName;
    }
    public void setlName(String lName) {
        this.lName = lName;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public String getAddress1() {
        return address1;
    }
    public void setAddress1(String address1) {
        this.address1 = address1;
    }
    public String getAddress2() {
        return address2;
    }
    public void setAddress2(String address2) {
        this.address2 = address2;
    }
    public String getMobileNo() {
        return mobileNo;
    }
    public void setMobileNo(String mobileNo) {
        this.mobileNo = mobileNo;
    }
}

and converting code is :

public static void main(String[] args) throws Throwable {
    List<String> param = new ArrayList<String>();
    param.add("fnameValue");
    param.add("lNameValue");
    param.add("genderValue");
    param.add("address1Value");
    param.add("address2Value");
    param.add("mobileNoValue");
    CreateCustomerRequest object = convert(param, CreateCustomerRequest.class);
    System.out.println("Gender : " + object.getGender());
}

public static <T extends Object> T convert(List<String> param, Class<T> clazz) throws Throwable
{
    Constructor<?> ctor = clazz.getConstructor();
    T result = (T) ctor.newInstance();
    Field[] fields = result.getClass().getDeclaredFields();
    if(fields == null)
        return null;

    for(int i =0;i<fields.length;i++)
    {           
        if(fields[i].getType().equals(String.class))
        {
            if(param.size() > i)
            {
                fields[i].setAccessible(true);
                fields[i].set(result, param.get(i));
            }
        }
    }       
    return result;
}

@ShiladittyaChakraborty You're welcome. I updated my answer for getting value (in proper way) If I understand your comment correctly. — Mehdi Tahmasebi, Sep 01 '18 at 04:45

score 2 · Answer 2 · answered Aug 30 '18 at 05:51

Say you have object and you want to get fields of class of that object, you can use reflection in following way to get list of those fields,

Field[] fields = createCustomerRequestObject.getClass().getDeclaredFields();
//OR
//Field[] fields = CreateCustomerRequest.class.getDeclaredFields();
List<String> fieldNames = new ArrayList<>();
for (Field field : fields) {
    fieldNames.add(field.getName());
}
System.out.println(fieldNames);

OUTPUT

[fName, lName, gender, address1, address2, mobileNo]

Thanx for this. Is there any way for getting the value also – Shiladittya Chakraborty Aug 30 '18 at 10:24 — Shiladittya Chakraborty, Aug 30 '18 at 10:24

Convert DTO to List of parameter

2 Answers2