在纯Java代码中输出HTML时,是否有一种推荐的方法来转义<,>,"和&字符?(除了手动执行以下操作之外)。

String source = "The less than sign (<) and ampersand (&) must be escaped before using them in HTML";
String escaped = source.replace("<", "&lt;").replace("&", "&amp;"); // ...

当前回答

Be careful with this. There are a number of different 'contexts' within an HTML document: Inside an element, quoted attribute value, unquoted attribute value, URL attribute, javascript, CSS, etc... You'll need to use a different encoding method for each of these to prevent Cross-Site Scripting (XSS). Check the OWASP XSS Prevention Cheat Sheet for details on each of these contexts. You can find escaping methods for each of these contexts in the OWASP ESAPI library -- https://github.com/ESAPI/esapi-java-legacy.

其他回答

对于使用谷歌番石榴的人:

import com.google.common.html.HtmlEscapers;
[...]
String source = "The less than sign (<) and ampersand (&) must be escaped before using them in HTML";
String escaped = HtmlEscapers.htmlEscaper().escape(source);

StringEscapeUtils from Apache Commons Lang:

import static org.apache.commons.lang.StringEscapeUtils.escapeHtml;
// ...
String source = "The less than sign (<) and ampersand (&) must be escaped before using them in HTML";
String escaped = escapeHtml(source);

版本3:

import static org.apache.commons.lang3.StringEscapeUtils.escapeHtml4;
// ...
String escaped = escapeHtml4(source);

Apache Commons的替代方案:使用Spring的htmltils。htmlEscape(字符串输入)方法。

出于某些目的,htmltils:

import org.springframework.web.util.HtmlUtils;
[...]
HtmlUtils.htmlEscapeDecimal("&"); //gives &#38;
HtmlUtils.htmlEscape("&"); //gives &amp;

Java 8+解决方案:

public static String escapeHTML(String str) {
    return str.chars().mapToObj(c -> c > 127 || "\"'<>&".indexOf(c) != -1 ?
       "&#" + c + ";" : String.valueOf((char) c)).collect(Collectors.joining());
}

String#chars返回String中的char值的IntStream。然后,我们可以使用mapToObj来转义字符代码大于127的字符(非ascii字符)以及双引号(")、单引号(')、左尖括号(<)、右尖括号(>)和&号(&)。收藏家。join将字符串连接在一起。

为了更好地处理Unicode字符,可以使用String#codePoints代替。

public static String escapeHTML(String str) {
    return str.codePoints().mapToObj(c -> c > 127 || "\"'<>&".indexOf(c) != -1 ?
            "&#" + c + ";" : new String(Character.toChars(c)))
       .collect(Collectors.joining());
}