在Java 8中从Pojo中删除不可打印的字符

Question

I want to remove the non-printable character only for the String fields in the poject, I know we can use

public String removeNonPrintable(String field) {
    return field.replaceAll("[^A-Za-z0-9]", "");
}

to remove the non-printable characters from string.

But I want to have the generic method like:

public <T> T removeNonPrintable(Class<T> myClassObject) {
    /// Get only the string and remove non-printable code stuffs
    return removedNonPrintableCharactersmyClassObject;
}

Can anyone please help me to do it?

This question may be duplicate, but I failed to found the exact solutions for it.

Answer 1

You could use reflection, which would be problematic and not guaranteed to work for fields that have deep structures.

Or you could just run the instance through your code:

public String removeNonPrintable(Object obj) {
    return String.valueOf(obj).replaceAll("[^A-Za-z0-9]", "");
}

Note: String.valueOf() is used to avoid having to deal with obj being null .

You might have more success if you changed the transformation to:

replaceAll("[^ -~]", "")

which will remove everything not a "regular" ascii char (ie between decimal 32 and 126 inclusive).

Answer 2

Following is working:

public static void removeNonPrintable(Node node) throws NoSuchFieldException, IllegalAccessException{
        Field[] fields = Node.class.getDeclaredFields();
        for(int i=0;i<fields.length;i++){
            if(fields[i].getType().equals(String.class)) {
                fields[i].set(node, removeNonPrintable(fields[i].get(node).toString()));
                System.out.println(fields[i].get(node));
            }
        }
    }

class Node{
     String left;
     String right;
     int data;
    public Node(String left, String right, Integer data){
        this.left = left;
        this.right = right;
        this.data = data;
    }
}

It will work for a particular class(eg Node). I am trying to make it work with Class<T> but it's giving some exception right now.

Answer 3

You can do it using reflection , but it is not recommended:-

public static void main(String[] args) throws IllegalAccessException {
    Person person = new Person();
    person.setName("John***");
    person.setAge(12);

    final Field[] fields = person.getClass().getDeclaredFields();
    for (Field field : fields) {
        if (field.getType() == String.class) {
            field.set(person, removeNonPrintable((String) field.get(person)));
        }
    }
    System.out.println(person.getName());
    System.out.println(person.getAge());
}

//using the regex provided by OP
private static String removeNonPrintable(String s) {
    return s.replaceAll("[^A-Za-z0-9]", "");
}

And you'll have to change String fields to public accessor. This prints:-

John
12

A better approach is to do this in getters or setters of String fields.

Example:-

public String getName() {
    return removeNonPrintable(name);
}

OR

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