Question

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!

Answer 1

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!");
}