Request.getParameterMap values not castable to string

01.JAVA/Java

Request.getParameterMap values not castable to string

1010 2013. 8. 6. 17:37

i am trying to get the complete parameter map from the request object and iterate over it.

here is the sample code

  Map map = request.getParameterMap();
for(Object key : map.keySet()){
    String keyStr = (String)key;
    Object value = map.get(keyStr);     
    System.out.println("Key " + (String)key + "     :    " + value);
}

output

  Key businessunit     :    [Ljava.lang.String;@388f8321
   Key site     :    [Ljava.lang.String;@55ea0889
  Key startDate     :    [Ljava.lang.String;@77d6866f
  Key submit     :    [Ljava.lang.String;@25141ee0
  Key traffictype     :    [Ljava.lang.String;@4bf71724

its evident from the output that the value object is an instance of String

now when i change my code to something like this

  Map map = request.getParameterMap();
  for(Object key : map.keySet()){
    String keyStr = (String)key;
    Object value = map.get(keyStr);
    if(value instanceof String)
    System.out.println("Key " + (String)key + "     :    " + (String)value);
}

it prints nothing but as per the previous output it should have printed the values and if i remove instanceOf check it gives ClassCastException. is this the expected behavior or i am doing something wrong here ?

asked Dec 5 '11 at 7:29

DPS
7431024

	Three possibilities: 1. Did you redeclare class `String` somewhere (try using `java.lang.String` instead of `String` to find out)? 2. Are you using the exact same values when running the two pieces of code? 3. Try using `String.valueOf(value)` or `value.toString()` and see what happens. Hope it helps. – The Nail Dec 5 '11 at 7:34
	Ah forget the above, it's an array. Fooled me. – The Nail Dec 5 '11 at 7:36

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3 Answers

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up vote4down voteaccepted

[Ljava.lang.String;@XXXXXXX means it is array of String not a single String. So your condition fails and it does not print anything.

answered Dec 5 '11 at 7:33

Harry Joy
22k853108

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up vote2down vote

The value is an array. If you're sure that the array is not empty, you should get the string value like this:

String value = (String) map.get(keyStr)[0];

answered Dec 5 '11 at 7:36

DavidLee
213

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up vote1down vote

As the object which is returned is an array of strings as Harry Joy pointed out, you will have to use the Arrays.toString() method in order to convert that array to a printable string:

    Map map = request.getParameterMap();
    for (Object key: map.keySet())
    {
            String keyStr = (String)key;
            String[] value = (String[])map.get(keyStr);
            System.out.println("Key" + (String)key + "   :   " + Arrays.toString(value));
    }