Java replace issues with ' (apostrophe/single quote) and \ (backslash) together

java string replace escaping backslash
derekmw picture derekmw · Jun 6, 2011 · Viewed 109k times · Source

I seem to be having issues. I have a query string that has values that can contain single quotes. This will break the query string. So I was trying to do a replace to change ' to \'.

Here is a sample code:

"This is' it".replace("'", "\'");

The output for this is still:

"This is' it".

It thinks I am just doing an escape character for the quote.

So I tried these two pieces of code:

"This is' it".replace("'", "\\'");  // \\ for the backslash, and a ' char
"This is' it".replace("'", "\\\'"); // \\ for the backslash, and \' for the ' char

Both of the above STILL results in the same output:

"This is' it"

I can only seem to get this to actually spit out a slash with:

"This is' it".replace("'", "\\\\'");

Which results in:

"This is\\' it"

Any suggestions? I just want to replace a ' with \'.

It doesn't seem like it should be that difficult.

Answer

Asaph picture Asaph · Jun 6, 2011

First of all, if you are trying to encode apostophes for querystrings, they need to be URLEncoded, not escaped with a leading backslash. For that use URLEncoder.encode(String, String) (BTW: the second argument should always be "UTF-8"). Secondly, if you want to replace all instances of apostophe with backslash apostrophe, you must escape the backslash in your string expression with a leading backslash. Like this:

"This is' it".replace("'", "\\'");

Edit:

I see now that you are probably trying to dynamically build a SQL statement. Do not do it this way. Your code will be susceptible to SQL injection attacks. Instead use a PreparedStatement.

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