Replacing a line in java from a substring using regex

Question

Say I have a multiple files which look like follows, and I'm looping through storing them in a variable called 'text':

<Property name="FirstProp"><![CDATA[  ]]></PackageProperty>
<Property name="SecondProp"><![CDATA[  ]]></PackageProperty>
<Property name="ThirdProp"><![CDATA[  ]]></PackageProperty>

Some of the files can have CDATA in them, so the only thing each has in common is the property name. I've stored the PropertyNames in a String array called propNames[ ]. So, "SecondProp" would be propNames[1].

I now want to replace the second line to include some CDATA, I've tried this but it doesn't work because I only want it to look before and after the current line, not the entire file.

String CDATAReplacement = "<Property name=\"SecondProp\"><![CDATA[ Some Value ]]></PackageProperty>";
text.replaceAll( "(.*)"+propNames[1]+"(.*)", CDATAReplacement )

End result:

<Property name="FirstProp"><![CDATA[  ]]></PackageProperty>
<Property name="SecondProp"><![CDATA[ Some Value ]]></PackageProperty>
<Property name="ThirdProp"><![CDATA[  ]]></PackageProperty>

I could do this quite easily using sed and execute the script within the java program, but I know it's bad practise so a Java solution would be better.

Given that it's manipulating XML, have you tried using an XML library? I'm not a Java native, so can't help you there, but for this task in .Net I'd be looking at using the XML classes to both read and update this data — James Thorpe
– James Thorpe, Commented Nov 24, 2014 at 16:30
I'm not sure I understand what you mean before and after current line not entire file? If the file is stored in text then replaceAll will look at entire file. — brso05
– brso05, Commented Nov 24, 2014 at 16:39

destudent · Accepted Answer · 2014-11-25 00:09:44Z

1

I would recommend you to use JDOM Library to work with XML: http://www.studytrails.com/java/xml/jdom2/java-xml-jdom2-xpath.jsp. So you can work through XPath instead of regexps .

edited Nov 25, 2014 at 0:09

answered Nov 24, 2014 at 17:03

destudent

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user254948 · Accepted Answer · 2014-11-24 16:43:14Z

First of all since it's xml I would recommend a xml manipulation library. However if you still want to use regex, I would recommend atleast validating the line a bit more so you dont end up replacing a line which happens to have the the name "SecondProp" in its value, or as part of its own name.

If you loaded the file normally with line endings, your code should however work. By default regular expressions in java are limited lines, Multi-line mode is off by default.

Here's a an example of a better matching regular expression though.

String regex =  "<property name=\"" + propertyName + "\"><!\\[CDATA\\[" + "([\s]*)" + "\\]\\]>" + "</packageProperty>";

Example:

String line = "<property name=\"SecondProp\"><![CDATA[   ]]></packageProperty>";
String propertyname = "SecondProp";
String CDATAReplacement = "<Property name=\"SecondProp\"><![CDATA[ Some Value ]]></PackageProperty>";
String regex =  "<property name=\"" + propertyName + "\"><!\\[CDATA\\[" + "([\s]*)" + "\\]\\]>" + "</packageProperty>";
System.out.println(line);
System.out.println(line.replaceAll(regex,CDATAReplacement));

brso05 · Accepted Answer · 2014-11-24 16:47:19Z

0

String test = "<Property name=\"FirstProp\"><![CDATA[  ]]></PackageProperty>\n<Property name=\"SecondProp\"><![CDATA[  ]]></PackageProperty>\n<Property name=\"ThirdProp\"><![CDATA[  ]]></PackageProperty>";
String test1 = "<Property name=\"SecondProp\"><![CDATA[ Some Value ]]></PackageProperty>";
test = test.replaceAll(".*SecondProp.*", test1);
System.out.println(test);

This should work the resulting output for this code is:

<Property name="FirstProp"><![CDATA[  ]]></PackageProperty>
<Property name="SecondProp"><![CDATA[ Some Value ]]></PackageProperty>
<Property name="ThirdProp"><![CDATA[  ]]></PackageProperty>

answered Nov 24, 2014 at 16:47

brso05

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