java - 字符串内容相同但 equals 方法返回 false

Question

我正在使用 StringEscapeUtils 转义和取消转义 html。我有以下代码

import org.apache.commons.lang.StringEscapeUtils;

public class EscapeUtils {

    public static void main(String args[]) {

        String string = "    4-Spaces    ,\"Double Quote\", 'Single Quote', \\Back-Slash\\, /Forward Slash/ ";

        String escaped = StringEscapeUtils.escapeHtml(string);
        String myEscaped = escapeHtml(string);

        String unescaped = StringEscapeUtils.unescapeHtml(escaped);
        String myUnescaped = StringEscapeUtils.unescapeHtml(myEscaped);

        System.out.println("Real String: " + string);
        System.out.println();
        System.out.println("Escaped String: " + escaped);
        System.out.println("My Escaped String: " + myEscaped);
        System.out.println();
        System.out.println("Unescaped String: " + unescaped);
        System.out.println("My Unescaped String: " + myUnescaped);
        System.out.println();
        System.out.println("Comparison:");
        System.out.println("Real String == Unescaped String: " + string.equals(unescaped));
        System.out.println("Real String == My Unescaped String: " + string.equals(myUnescaped));
        System.out.println("Unescaped String == My Unescaped String: " + unescaped.equals(myUnescaped));

    }

    public static String escapeHtml(String s) {
        String escaped = "";
        if(null != s) {
            escaped = StringEscapeUtils.escapeHtml(s);
            escaped = escaped.replaceAll(" "," ");
            escaped = escaped.replaceAll("'","'");
            escaped = escaped.replaceAll("\\\\","\");
            escaped = escaped.replaceAll("/","/");
        }
        return escaped;
    }

}

输出:

Real String:     4-Spaces    ,"Double Quote", 'Single Quote', \Back-Slash\, /Forward Slash/ 

Escaped String:     4-Spaces    ,"Double Quote", 'Single Quote', \Back-Slash\, /Forward Slash/ 
My Escaped String:     4-Spaces    ,"Double Quote", 'Single Quote', \Back-Slash\, /Forward Slash/ 

Unescaped String:     4-Spaces    ,"Double Quote", 'Single Quote', \Back-Slash\, /Forward Slash/ 
My Unescaped String:     4-Spaces    ,"Double Quote", 'Single Quote', \Back-Slash\, /Forward Slash/ 

Comparison:
Real String == Unescaped String: true
Real String == My Unescaped String: false
Unescaped String == My Unescaped String: false

我转义真正的字符串然后取消转义。但是 myEsceped 首先使用相同的过程进行转义，然后将更多的 html 字符替换为它们的 html 代码。 myUnescaped 实际上是对myEscaped 的转义，与真正的字符串内容相同。

输出显示真实的string、unescaped 和myUnescaped 内容相同。但是，在比较部分，myUnescaped 不等于 string 和 unescaped。

我还不明白这里到底发生了什么。谁能解释一下？

Answer 1

这是因为在转义 HTML 时，您将 ' ' 替换为  

public static String escapeHtml(String s) {
        String escaped = "";
        if(null != s) {
            escaped = StringEscapeUtils.escapeHtml(s);
            escaped = escaped.replaceAll(" "," "); // HERE
            escaped = escaped.replaceAll("'","'");
            escaped = escaped.replaceAll("\\\\","\");
            escaped = escaped.replaceAll("/","/");
        }
        return escaped;
    }

同时 StringEscapeUtils.escapeHtml不会转义 ' '，下面是他们网站上的例子:

"bread" & "butter" 

成为

"bread" & "butter"

这意味着 StringEscapeUtils.escapeHtml 保留空格

如果从 escapeHtml 中删除 escaped = escaped.replaceAll(""," ");, unescaped 和 myUnescaped 匹配!