详解xml型字符串解析时存在& < >符号时的解决方案

The entityname must immediately follow the '&' in the entity reference

public void chartReplace(){
        String str2 = "<logentry revision=&#39;1&#39;>" +
                "<msg>In this comment, I fixed a <bug>, and <added> file1&&file2.</msg>" +
                "</logentry>";
        System.out.println("original string: "+str2);
         
        //替换“&”：$1表示与(<msg>.*)的匹配子序列；$4表示与(.*</msg>)匹配的。
                     //&(?!amp;)表示匹配&而且后面不是amp;的字符串
        //"$1&$3$4"得到的结果就是替换了<msg></msg>中的“&”为“&”
        //由于每次只能替换掉一个“&”，所以循环执行替换，直到替换后与替换前的字符串相等。
        String str1 = "";
        while(!str2.equals(str1)){
            str1 = str2;
            str2 = str1.replaceAll("(<msg>.*)(&(?!amp;))(.*</msg>)", "$1&$3");
        }
        System.out.println("firstly replace \"&\": "+str2);
         
        //替换“<”
        str1 = "";
        while(!str2.equals(str1)){
            str1 = str2;
            str2 = str1.replaceAll("(<msg>.*)(<)(.*</msg>)", "$1<$3");
        }
        System.out.println("then replace \"<\": "+str2);
         
        //替换“<”
        str1 = "";
        while(!str2.equals(str1)){
            str1 = str2;
            str2 = str1.replaceAll("(<msg>.*)(>)(.*</msg>)", "$1>$3");
        }
        System.out.println("finally replace \">\": "+str2);
    }