Package org.apache.commons.lang

## Class StringEscapeUtils

- java.lang.Object
- - org.apache.commons.lang.StringEscapeUtils

-     public class StringEscapeUtils
      extends Object

  Escapes and unescapes `String`s for Java, Java Script, HTML, XML, and SQL.

  #ThreadSafe#

  Since:
    2.0
  Version:
    $Id: StringEscapeUtils.java 1057072 2011-01-10 01:55:57Z niallp $

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `StringEscapeUtils()` | `StringEscapeUtils` instances should NOT be constructed in standard programming.

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `static void` | `escapeCsv​(Writer out, String str)` | Writes a `String` value for a CSV column enclosed in double quotes, if required.
    `static String` | `escapeCsv​(String str)` | Returns a `String` value for a CSV column enclosed in double quotes, if required.
    `static void` | `escapeHtml​(Writer writer, String string)` | Escapes the characters in a `String` using HTML entities and writes them to a `Writer`.
    `static String` | `escapeHtml​(String str)` | Escapes the characters in a `String` using HTML entities.
    `static void` | `escapeJava​(Writer out, String str)` | Escapes the characters in a `String` using Java String rules to a `Writer`.
    `static String` | `escapeJava​(String str)` | Escapes the characters in a `String` using Java String rules.
    `static void` | `escapeJavaScript​(Writer out, String str)` | Escapes the characters in a `String` using JavaScript String rules to a `Writer`.
    `static String` | `escapeJavaScript​(String str)` | Escapes the characters in a `String` using JavaScript String rules.
    `static String` | `escapeSql​(String str)` | Escapes the characters in a `String` to be suitable to pass to an SQL query.
    `static void` | `escapeXml​(Writer writer, String str)` | Escapes the characters in a `String` using XML entities.
    `static String` | `escapeXml​(String str)` | Escapes the characters in a `String` using XML entities.
    `static void` | `unescapeCsv​(Writer out, String str)` | Returns a `String` value for an unescaped CSV column.
    `static String` | `unescapeCsv​(String str)` | Returns a `String` value for an unescaped CSV column.
    `static void` | `unescapeHtml​(Writer writer, String string)` | Unescapes a string containing entity escapes to a string containing the actual Unicode characters corresponding to the escapes.
    `static String` | `unescapeHtml​(String str)` | Unescapes a string containing entity escapes to a string containing the actual Unicode characters corresponding to the escapes.
    `static void` | `unescapeJava​(Writer out, String str)` | Unescapes any Java literals found in the `String` to a `Writer`.
    `static String` | `unescapeJava​(String str)` | Unescapes any Java literals found in the `String`.
    `static void` | `unescapeJavaScript​(Writer out, String str)` | Unescapes any JavaScript literals found in the `String` to a `Writer`.
    `static String` | `unescapeJavaScript​(String str)` | Unescapes any JavaScript literals found in the `String`.
    `static void` | `unescapeXml​(Writer writer, String str)` | Unescapes a string containing XML entity escapes to a string containing the actual Unicode characters corresponding to the escapes.
    `static String` | `unescapeXml​(String str)` | Unescapes a string containing XML entity escapes to a string containing the actual Unicode characters corresponding to the escapes.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### StringEscapeUtils

          public StringEscapeUtils()

      `StringEscapeUtils` instances should NOT be constructed in standard programming.

      Instead, the class should be used as:

          StringEscapeUtils.escapeJava("foo");

      This constructor is public to permit tools that require a JavaBean instance to operate.

  - ### Method Detail

    - #### escapeJava

          public static String escapeJava​(String str)

      Escapes the characters in a `String` using Java String rules.

      Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.)

      So a tab becomes the characters `'\\'` and `'t'`.

      The only difference between Java strings and JavaScript strings is that in JavaScript, a single quote must be escaped.

      Example:

           input string: He didn't say, "Stop!"
           output string: He didn't say, \"Stop!\"

      Parameters:
        `str` - String to escape values in, may be null
      Returns:
        String with escaped values, `null` if null string input

    - #### escapeJava

          public static void escapeJava​(Writer out,
                                        String str)
                                 throws IOException

      Escapes the characters in a `String` using Java String rules to a `Writer`.

      A `null` string input has no effect.

      Parameters:
        `out` - Writer to write escaped string into
        `str` - String to escape values in, may be null
      Throws:
        `IllegalArgumentException` - if the Writer is `null`
        `IOException` - if error occurs on underlying Writer
      See Also:
        `escapeJava(java.lang.String)`

    - #### escapeJavaScript

          public static String escapeJavaScript​(String str)

      Escapes the characters in a `String` using JavaScript String rules.

      Escapes any values it finds into their JavaScript String form. Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.)

      So a tab becomes the characters `'\\'` and `'t'`.

      The only difference between Java strings and JavaScript strings is that in JavaScript, a single quote must be escaped.

      Example:

           input string: He didn't say, "Stop!"
           output string: He didn\'t say, \"Stop!\"

      Parameters:
        `str` - String to escape values in, may be null
      Returns:
        String with escaped values, `null` if null string input

    - #### escapeJavaScript

          public static void escapeJavaScript​(Writer out,
                                              String str)
                                       throws IOException

      Escapes the characters in a `String` using JavaScript String rules to a `Writer`.

      A `null` string input has no effect.

      Parameters:
        `out` - Writer to write escaped string into
        `str` - String to escape values in, may be null
      Throws:
        `IllegalArgumentException` - if the Writer is `null`
        `IOException` - if error occurs on underlying Writer
      See Also:
        `escapeJavaScript(java.lang.String)`

    - #### unescapeJava

          public static String unescapeJava​(String str)

      Unescapes any Java literals found in the `String`. For example, it will turn a sequence of `'\'` and `'n'` into a newline character, unless the `'\'` is preceded by another `'\'`.

      Parameters:
        `str` - the `String` to unescape, may be null
      Returns:
        a new unescaped `String`, `null` if null string input

    - #### unescapeJava

          public static void unescapeJava​(Writer out,
                                          String str)
                                   throws IOException

      Unescapes any Java literals found in the `String` to a `Writer`.

      For example, it will turn a sequence of `'\'` and `'n'` into a newline character, unless the `'\'` is preceded by another `'\'`.

      A `null` string input has no effect.

      Parameters:
        `out` - the `Writer` used to output unescaped characters
        `str` - the `String` to unescape, may be null
      Throws:
        `IllegalArgumentException` - if the Writer is `null`
        `IOException` - if error occurs on underlying Writer

    - #### unescapeJavaScript

          public static String unescapeJavaScript​(String str)

      Unescapes any JavaScript literals found in the `String`.

      For example, it will turn a sequence of `'\'` and `'n'` into a newline character, unless the `'\'` is preceded by another `'\'`.

      Parameters:
        `str` - the `String` to unescape, may be null
      Returns:
        A new unescaped `String`, `null` if null string input
      See Also:
        `unescapeJava(String)`

    - #### unescapeJavaScript

          public static void unescapeJavaScript​(Writer out,
                                                String str)
                                         throws IOException

      Unescapes any JavaScript literals found in the `String` to a `Writer`.

      For example, it will turn a sequence of `'\'` and `'n'` into a newline character, unless the `'\'` is preceded by another `'\'`.

      A `null` string input has no effect.

      Parameters:
        `out` - the `Writer` used to output unescaped characters
        `str` - the `String` to unescape, may be null
      Throws:
        `IllegalArgumentException` - if the Writer is `null`
        `IOException` - if error occurs on underlying Writer
      See Also:
        `unescapeJava(Writer,String)`

    - #### escapeHtml

          public static String escapeHtml​(String str)

      Escapes the characters in a `String` using HTML entities.

      For example:

      `"bread" & "butter"`

      becomes:

      `&quot;bread&quot; &amp; &quot;butter&quot;`.

      Supports all known HTML 4.0 entities, including funky accents. Note that the commonly used apostrophe escape character (&apos;) is not a legal entity and so is not supported).

      Parameters:
        `str` - the `String` to escape, may be null
      Returns:
        a new escaped `String`, `null` if null string input
      See Also:
        `unescapeHtml(String)`, ISO Entities, HTML 3.2 Character Entities for ISO Latin-1, HTML 4.0 Character entity references, HTML 4.01 Character References, HTML 4.01 Code positions

    - #### escapeHtml

          public static void escapeHtml​(Writer writer,
                                        String string)
                                 throws IOException

      Escapes the characters in a `String` using HTML entities and writes them to a `Writer`.

      For example:

      `"bread" & "butter"`

      becomes:

      `&quot;bread&quot; &amp; &quot;butter&quot;`.

      Supports all known HTML 4.0 entities, including funky accents. Note that the commonly used apostrophe escape character (&apos;) is not a legal entity and so is not supported).

      Parameters:
        `writer` - the writer receiving the escaped string, not null
        `string` - the `String` to escape, may be null
      Throws:
        `IllegalArgumentException` - if the writer is null
        `IOException` - when `Writer` passed throws the exception from calls to the `Writer.write(int)` methods.
      See Also:
        `escapeHtml(String)`, `unescapeHtml(String)`, ISO Entities, HTML 3.2 Character Entities for ISO Latin-1, HTML 4.0 Character entity references, HTML 4.01 Character References, HTML 4.01 Code positions

    - #### unescapeHtml

          public static String unescapeHtml​(String str)

      Unescapes a string containing entity escapes to a string containing the actual Unicode characters corresponding to the escapes. Supports HTML 4.0 entities.

      For example, the string "&lt;Fran&ccedil;ais&gt;" will become "<Français>"

      If an entity is unrecognized, it is left alone, and inserted verbatim into the result string. e.g. "&gt;&zzzz;x" will become ">&zzzz;x".

      Parameters:
        `str` - the `String` to unescape, may be null
      Returns:
        a new unescaped `String`, `null` if null string input
      See Also:
        `escapeHtml(Writer, String)`

    - #### unescapeHtml

          public static void unescapeHtml​(Writer writer,
                                          String string)
                                   throws IOException

      Unescapes a string containing entity escapes to a string containing the actual Unicode characters corresponding to the escapes. Supports HTML 4.0 entities.

      For example, the string "&lt;Fran&ccedil;ais&gt;" will become "<Français>"

      If an entity is unrecognized, it is left alone, and inserted verbatim into the result string. e.g. "&gt;&zzzz;x" will become ">&zzzz;x".

      Parameters:
        `writer` - the writer receiving the unescaped string, not null
        `string` - the `String` to unescape, may be null
      Throws:
        `IllegalArgumentException` - if the writer is null
        `IOException` - if an IOException occurs
      See Also:
        `escapeHtml(String)`

    - #### escapeXml

          public static void escapeXml​(Writer writer,
                                       String str)
                                throws IOException

      Escapes the characters in a `String` using XML entities.

      For example: `"bread" & "butter"` => `&quot;bread&quot; &amp; &quot;butter&quot;`.

      Supports only the five basic XML entities (gt, lt, quot, amp, apos). Does not support DTDs or external entities.

      Note that unicode characters greater than 0x7f are currently escaped to their numerical \\u equivalent. This may change in future releases.

      Parameters:
        `writer` - the writer receiving the unescaped string, not null
        `str` - the `String` to escape, may be null
      Throws:
        `IllegalArgumentException` - if the writer is null
        `IOException` - if there is a problem writing
      See Also:
        `unescapeXml(java.lang.String)`

    - #### escapeXml

          public static String escapeXml​(String str)

      Escapes the characters in a `String` using XML entities.

      For example: `"bread" & "butter"` => `&quot;bread&quot; &amp; &quot;butter&quot;`.

      Supports only the five basic XML entities (gt, lt, quot, amp, apos). Does not support DTDs or external entities.

      Note that unicode characters greater than 0x7f are currently escaped to their numerical \\u equivalent. This may change in future releases.

      Parameters:
        `str` - the `String` to escape, may be null
      Returns:
        a new escaped `String`, `null` if null string input
      See Also:
        `unescapeXml(java.lang.String)`

    - #### unescapeXml

          public static void unescapeXml​(Writer writer,
                                         String str)
                                  throws IOException

      Unescapes a string containing XML entity escapes to a string containing the actual Unicode characters corresponding to the escapes.

      Supports only the five basic XML entities (gt, lt, quot, amp, apos). Does not support DTDs or external entities.

      Note that numerical \\u unicode codes are unescaped to their respective unicode characters. This may change in future releases.

      Parameters:
        `writer` - the writer receiving the unescaped string, not null
        `str` - the `String` to unescape, may be null
      Throws:
        `IllegalArgumentException` - if the writer is null
        `IOException` - if there is a problem writing
      See Also:
        `escapeXml(String)`

    - #### unescapeXml

          public static String unescapeXml​(String str)

      Unescapes a string containing XML entity escapes to a string containing the actual Unicode characters corresponding to the escapes.

      Supports only the five basic XML entities (gt, lt, quot, amp, apos). Does not support DTDs or external entities.

      Note that numerical \\u unicode codes are unescaped to their respective unicode characters. This may change in future releases.

      Parameters:
        `str` - the `String` to unescape, may be null
      Returns:
        a new unescaped `String`, `null` if null string input
      See Also:
        `escapeXml(String)`

    - #### escapeSql

          public static String escapeSql​(String str)

      Escapes the characters in a `String` to be suitable to pass to an SQL query.

      For example,

          statement.executeQuery("SELECT * FROM MOVIES WHERE TITLE='" +
             StringEscapeUtils.escapeSql("McHale's Navy") +
             "'");

      At present, this method only turns single-quotes into doubled single-quotes (`"McHale's Navy"` => `"McHale''s Navy"`). It does not handle the cases of percent (%) or underscore (_) for use in LIKE clauses.

      see http://www.jguru.com/faq/view.jsp?EID=8881
      Parameters:
        `str` - the string to escape, may be null
      Returns:
        a new String, escaped for SQL, `null` if null string input

    - #### escapeCsv

          public static String escapeCsv​(String str)

      Returns a `String` value for a CSV column enclosed in double quotes, if required.

      If the value contains a comma, newline or double quote, then the String value is returned enclosed in double quotes.

      Any double quote characters in the value are escaped with another double quote.

      If the value does not contain a comma, newline or double quote, then the String value is returned unchanged.

      see Wikipedia and RFC 4180.
      Parameters:
        `str` - the input CSV column String, may be null
      Returns:
        the input String, enclosed in double quotes if the value contains a comma, newline or double quote, `null` if null string input
      Since:
        2.4

    - #### escapeCsv

          public static void escapeCsv​(Writer out,
                                       String str)
                                throws IOException

      Writes a `String` value for a CSV column enclosed in double quotes, if required.

      If the value contains a comma, newline or double quote, then the String value is written enclosed in double quotes.

      Any double quote characters in the value are escaped with another double quote.

      If the value does not contain a comma, newline or double quote, then the String value is written unchanged (null values are ignored).

      see Wikipedia and RFC 4180.
      Parameters:
        `str` - the input CSV column String, may be null
        `out` - Writer to write input string to, enclosed in double quotes if it contains a comma, newline or double quote
      Throws:
        `IOException` - if error occurs on underlying Writer
      Since:
        2.4

    - #### unescapeCsv

          public static String unescapeCsv​(String str)

      Returns a `String` value for an unescaped CSV column.

      If the value is enclosed in double quotes, and contains a comma, newline or double quote, then quotes are removed.

      Any double quote escaped characters (a pair of double quotes) are unescaped to just one double quote.

      If the value is not enclosed in double quotes, or is and does not contain a comma, newline or double quote, then the String value is returned unchanged.

      see Wikipedia and RFC 4180.
      Parameters:
        `str` - the input CSV column String, may be null
      Returns:
        the input String, with enclosing double quotes removed and embedded double quotes unescaped, `null` if null string input
      Since:
        2.4

    - #### unescapeCsv

          public static void unescapeCsv​(Writer out,
                                         String str)
                                  throws IOException

      Returns a `String` value for an unescaped CSV column.

      If the value is enclosed in double quotes, and contains a comma, newline or double quote, then quotes are removed.

      Any double quote escaped characters (a pair of double quotes) are unescaped to just one double quote.

      If the value is not enclosed in double quotes, or is and does not contain a comma, newline or double quote, then the String value is returned unchanged.

      see Wikipedia and RFC 4180.
      Parameters:
        `str` - the input CSV column String, may be null
        `out` - Writer to write the input String to, with enclosing double quotes removed and embedded double quotes unescaped, `null` if null string input
      Throws:
        `IOException` - if error occurs on underlying Writer
      Since:
        2.4