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I need to use Java to replace some JavaScript in a file. The steps I'm taking are basically like this:

  1. Read in a file (it's an .asp file with JavaScript in it that is generated from another system)
  2. Replace the unwanted JavaScript function with one I do want
  3. Write it back out over the file that was originally generated

I'm having trouble with step 2 because my code seems to freak out on the replaceAll method. Let's say I want to replace this method:

function sayHi() {
    alert('hi');
}

...with something like this:

function sayHi() {
    alert("Hello, World!");
}

I have code that looks like this:

private static final String REPLACEMENT_METHOD =
        "function sayHi() {\n" +
        "   alert('Hello, World!');\n" +
        "}";

private static final String METHOD_TO_REPLACE =
        "function sayHi() {\n" +
        "   alert('hi');\n" +
        "}";

String content = // Get the contents from the file...

content = content.replaceAll(METHOD_TO_REPLACE, REPLACEMENT_METHOD);

The problem I'm running into is that the string that I want to replace is being interpreted as a regex (it's just literal text, but it is, of course, interpreted as a regex) and it bails out on me. Unfortunately, I've not been able to find the correct syntax to escape the special characters properly and still get it to match the way I want.

Any ideas?

Thanks!

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  • Maybe you should try with a substring of the entire match and then slowly work towards the entire match: Start with a simpler METHOD_TO_REPLACE like "hello", and just a small part of REPLACEMENT_METHOD such as "function sayHi". If that works, then you can slowly increase the matching criteria until you figure what doesn't work. Commented Oct 11, 2012 at 21:20

3 Answers 3

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3

You can use quote operators around your match pattern:

private static final String METHOD_TO_REPLACE =
    "\\Q" +
    "function sayHi() {\n" +
    "   alert('hi');\n" +
    "}" +
    "\\E";

By the way,

function sayHi() {
    alert("Hello, World!");
}

isn't going to work in Java. You probably want:

void sayHi() {
    alert("Hello, World!");
}
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8 Comments

Nice, I didn't know about these quotes operators. About the sayHi function: he's using Javascript, there is no void, only function.
Beautiful! That allows me to do the replacement exactly as I wanted. I had been looking at the Pattern API and completely missed that part, but I see it there, now. Thanks!
@DanielPereira - OP said that the goal was to replace JavaScript functions with Java.
@TedHopp Yes, and sayHi is one of the Javascript functions he wants to replace, not a function written in Java.
@DanielPereira I was referring to REPLACEMENT_METHOD in the question; as I understand it, that's supposed to be the Java replacement.
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1

Method replaceAll indeed uses the first parameter as a pattern.

So, you have the following solutions.

  1. escape your patterns manually. As far as I can see it is not too hard in your case.
  2. try to do this programmatically using Pattern.quote()
  3. use String.replace() in loop instead of replaceAll(). Method replace() works with plain strings.
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Have you tried the backslash \?

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I have. The compiler seems to be complaining about the '{' on the first line - I get a "number expected" error. If I try to escape that and make it '\{', I get a new compiler error: "Illegal escape character in a string literal". If I add a second escape character, so it becomes '\\{', it compiles. Unfortunately, that changes my matching pattern to be "function sayHi() \{" and that won't match the way I want it to.

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