Java检查字段的特定值

Question

I have requirement to check for a particular field only particular values are allowed, how to do that best in java.

For example:

For a "Status" field only allowed values are "eq" and "in" For a "Date" field only allowed values are "gt","ge" and "eq"

My method will look something like this,

boolean checkFieldAndOperatorMatching(String field, String operator);

for example, if some one passes

 checkFieldAndOperatorMatching("status", "eq"); //correct
 checkFieldAndOperatorMatching("status", "in"); //correct

 checkFieldAndOperatorMatching("status", "gt"); // not correct

 checkFieldAndOperatorMatching("date", "gt"); //correct
 checkFieldAndOperatorMatching("date", "ge"); //correct
 checkFieldAndOperatorMatching("date", "eq"); //correct

 checkFieldAndOperatorMatching("date", "in"); // not correct

Answer 1

Using Properties, you can do similar(change to suit your requirements) to below:

    public boolean checkFieldAndOperatorMatching(String field, String operator) {

    // can be loaded once
    // make it static or use a factory method
    // which returns same Properties instance every time if already loaded
    Properties properties = new Properties();

    try (FileInputStream fin = new FileInputStream("D:\\fields.properties");) {

        properties.load(fin);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    String validValues = properties.getProperty(field);

    return Arrays.asList(validValues.split(",")).contains(operator);
}

where, fields.properties contains:

date=gt,ge,eq
status=eq,in

Answer 2

You can create Enums for Date and Status , which contains the permitted values:-

enum Status {
    eq,in
}
enum Date {
    gt,ge,eq
}

And then iterate through enum to check if the values passed in parameter exist in enums:-

static boolean checkFieldAndOperatorMatching(String field, String operator){

    if(field.equals("Status")){ //if field is Status

        for (Status s : Status.values()) {

             if(operator.equals(s.toString())){

                 return true;
             }

             }
             return false;
        }

     if(field.equals("Date")){ //if field is Date

         for (Date d : Date.values()) {
             if(operator.equals(d.toString())){

                 return true;
             }

         }
             return false;
      }

 }

Answer 3

if you have many fields for validation, you can do the following

• Use DB to store the key-values and caches those in Collections to validate (IF you have grow-able number of fields)

• Use Properties file to represent $field = $values ( comma separated) and read them in your validate method (If you have mostly static list of fields with constant values

• Use enums if its completely static values. I agree that it will make you write extra lines of code, but is one of the good practice to have constant field values in enums.