ToStringBuilder output makes it difficult to distinguich between an empty
String array and an array of one empty String
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Key: LANG-647
URL: https://issues.apache.org/jira/browse/LANG-647
Project: Commons Lang
Issue Type: Improvement
Components: lang.builder.*
Affects Versions: 2.5
Reporter: pascal jacob
Priority: Minor
ToStringBuilder output is the same for an empty array (i.e. new String[0]) and
for an array containing only a single empty string (i.e. new String[] { "" } ).
This makes it difficult in some case to see the true nature of arrays.
For example I once had a JUnit test case that print the following trace failure:
java.lang.AssertionError:
Expected: <InputViewHelper[a={},b={},c={msg},d={time}>
got: <InputViewHelper[a={},b={},c={msg},d={time}>
Apparently the two objects look like the same! But they are not: one had an
empty array; the other had an array with only a single empty string. With a
customized ToStringStyle the difference became apparent:
Expected: <InputViewHelper[a={},b={},c={msg},d={time}>
got: <InputViewHelper[a={""},b={},c={msg},d={time}>
The fix is simple, change the method: protected void appendDetail(StringBuffer
buffer, String fieldName, Object value) to:
protected void appendDetail(StringBuffer buffer, String
fieldName, Object value) {
if((value instanceof String) &&
((String)value).isEmpty()) {
buffer.append("\"\"");
}
else {
super.appendDetail(buffer, fieldName,
value);
}
}
here is the test case that revealed the problem:
public void testToStringBuilder() {
ToStringBuilder builder1 = new ToStringBuilder("Builder1");
builder1.append("empty array", new String[0]);
builder1.append("array of one empty string", new String[] { ""
});
builder1.append("array of two empty strings", new String[] {
"", "" });
String builder1Result = builder1.toString();
System.out.println(builder1Result);
// -----
ToStringBuilder builder2 = new ToStringBuilder("Builder2", new
ToStringStyle() {
@Override
protected void appendDetail(StringBuffer buffer, String
fieldName, Object value) {
if((value instanceof String) &&
((String)value).isEmpty()) {
buffer.append("\"\"");
}
else {
super.appendDetail(buffer, fieldName,
value);
}
}
});
builder2.append("empty array", new String[0]);
builder2.append("array of one empty string", new String[] { ""
});
builder2.append("array of two empty strings", new String[] {
"", "" });
String builder2Result = builder2.toString();
System.out.println(builder2Result);
}
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