这个问题在这里已经有答案了：

java preparedstatement utf-8字符问题（4个答案）
11天前关门了。
我使用的数据库有一个表，其中一个字段是用ipa字符编写的，例如一个字段是：/iː/ - /ɪ/
我正在做一个prepared语句，结果集是空的，不应该是空的（我检查了查询），当我打印prepared语句时，字符的编码有问题：

com.mysql.cj.jdbc.ClientPreparedStatement: SELECT Id, sound, pair, IPA, writed_word, pair_name FROM minimal_pair WHERE dismised <> 1 AND pair_name = '/i?/ - /?/'

pair\u name值应为：/iː/ - /ɪ/
查询数据库的方法代码为：

public static ArrayList<Word> returnRandomWordsFromPair(String pair_name) {

        ArrayList<Word> pairNameList = new ArrayList<Word>();

        // Connection variables
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        // Calling the connection
        conn = Dataconn.conn();

        String sql = "SELECT Id, sound, pair, IPA, writed_word, pair_name FROM minimal_pair WHERE dismised <> 1 AND pair_name = ?";
        System.out.println(sql);
        try {
            pstmt = conn.prepareStatement(sql);
            // The next line are the parameters
            pstmt.setString(1, pair_name);
            System.out.println(pstmt);
            rs = pstmt.executeQuery();
            while (rs.next()) {
                Word word = new Word();
                word.setId(rs.getInt("Id"));
                word.setSound(rs.getString("sound"));
                word.setPair(rs.getString("pair"));
                word.setIpa(rs.getString("IPA"));
                word.setWrited_word(rs.getString("writed_word"));
                word.setPair_name(rs.getString("pair_name"));

                pairNameList.add(word);
                System.out.println(word);
            }

            if (rs != null)
                System.out.println("result set is null");
                try {
                    rs.close();
                } catch (SQLException logIgnore) {
                }
            if (pstmt != null)
                System.out.println("prepared statement is null");
                try {
                    rs.close();
                } catch (SQLException logIgnore) {
                }
            if (conn != null)
                System.out.println("connection is null");
                try {
                    rs.close();
                } catch (SQLException logIgnore) {
                }

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if (rs != null)
                try {
                    rs.close();
                } catch (SQLException logIgnore) {
                }
            if (pstmt != null)
                try {
                    rs.close();
                } catch (SQLException logIgnore) {
                }
            if (conn != null)
                try {
                    rs.close();
                } catch (SQLException logIgnore) {
                }
        }

        Dataconn.closeConn(conn);

        return pairNameList;
    }

我从这个代码中调用它：

public static void main(String[] args) {

        ArrayList<Word> wordList = new ArrayList<Word>();

        wordList = DatabaseMethods.returnRandomWordsFromPair("/iː/ - /ɪ/");

        String name = wordList.getClass().getSimpleName();
        System.out.println(name);

        System.out.println(wordList);

        for (Word smallWord : wordList)
          {               
               System.out.println(smallWord.toString());        
          }
    }

标准输出结果为：

SELECT Id, sound, pair, IPA, writed_word, pair_name FROM minimal_pair WHERE dismised <> 1 AND pair_name = ?
com.mysql.cj.jdbc.ClientPreparedStatement: SELECT Id, sound, pair, IPA, writed_word, pair_name FROM minimal_pair WHERE dismised <> 1 AND pair_name = '/i?/ - /?/'
result set is null
prepared statement is null
connection is null
Connection closed
ArrayList
[]

我已经在函数中检查了string/iː/ - /ɪ/ 正确打印，但在执行准备好的语句时显示“/i？/-/？/”
有人知道为什么会这样，我该怎么解决？
事先非常感谢！