我们可以替换Java中的一部分字符串，其中包含开头和结尾的符号吗？

Question

我有一个字符串SELECT *FROM USERS WHERE ID = '@userid@' AND ROLE = '@role@'现在我已经用@实际值替换@ ... @之间的任何字符串。

预期产量SELECT *FROM USERS WHERE ID = '4' AND ROLE = 'Admin'

这个替换将从一个方法发生，我写了这个逻辑

public String replaceQueryKeyWithValueFromKeyValues(String query, int reportId) {
    try {
        REPMReportDao repmReportDao = new REPMReportDao();
        int Start = 0;
        int end;
        if (query.contains("@")) {
            boolean specialSymbolFound = false;
            for (int i = 0; i < query.length(); i++) {
                if (query.charAt(i) == '@') {
                    if (!specialSymbolFound) {
                        Start = i + 1;
                        specialSymbolFound = true;
                    } else {
                        specialSymbolFound = false;
                        end = i;
                        query = query.replace(query.substring(Start - 1, end + 1), repmReportDao.getReportManagerKeyValue(query.substring(Start - 1, end + 1).replaceAll("@", ""), reportId));

                    }
                }
            }
            return query;
        } else {
            return query;
        }

    } catch (Exception e) {
        logger.log(Priority.ERROR, e.getMessage());
        return e.getMessage();
    }
}

它工作正常，但如果存在单个'@'符号而不是开始和结束，它将失败。喜欢 ：

SELECT  *FROM USERS WHERE emailid = '[email protected]' AND ROLE = '@role@'

在这里，它应该替换唯一的角色'@ role @'，并且应该保留电子邮件原样。

预期产出=> SELECT *FROM USERS WHERE emailid = '[email protected]' AND ROLE = 'Admin'

Answer 1

getReportManagerKeyValue返回的模拟数据的完整示例：

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class StackOverflow54842971 {

    private static Map<String, String> map;

    public static void main(String[] args) {
        // preparing test data
        map = new HashMap<>();
        map.put("role", "Admin");
        map.put("userid", "666");

        // original query string
        String query = "SELECT * FROM USERS WHERE ID = '@userid@' AND emailid = '[email protected]' AND ROLE = '@role@' ";

        // regular expression to match everything between '@ and @' with capture group
        // omitting single quotes
        Pattern p = Pattern.compile("'(@[^@]*@)'");
        Matcher m = p.matcher(query);
        while (m.find()) {
            // every match will be replaced with value from getReportManagerKeyValue
            query = query.replace(m.group(1), getReportManagerKeyValue(m.group(1).replaceAll("@", "")));
        }
        System.out.println(query);
    }

    // you won't need this function
    private static String getReportManagerKeyValue(String key) {
        System.out.println("getting key " + key);
        if (!map.containsKey(key)) {
            return "'null'";
        }
        return map.get(key);
    }
}

Answer 2

使用字符串替换生成数据库查询被认为是非常糟糕的做法，因为您将代码保持为SQL注入攻击。我无法从您提供的小代码示例中看出，但绝大多数大型Java项目都使用Spring Framework，它允许您使用JdbcTemplate或（我的偏好）NamedParameterJdbcTemplate。两者都允许您以安全的方式替换变量。