jdbcTemplate.queryForList（sql，object，classType）的返回类型

Question

我正在以以下方式使用jdbcTemplate.queryForList执行命名查询：

List<Conversation> conversations = jdbcTemplate.queryForList(
            SELECT_ALL_CONVERSATIONS_SQL_FULL,
            new Object[] {userId, dateFrom, dateTo});

SQL查询为：

private final String SELECT_ALL_CONVERSATIONS_SQL_FULL = 
    "select conversation.conversationID, conversation.room, " +
    "conversation.isExternal, conversation.startDate, " +
    "conversation.lastActivity, conversation.messageCount " +
    "from openfire.ofconversation conversation " +
    "WHERE conversation.conversationid IN " +
    "(SELECT conversation.conversationID " +
    "FROM openfire.ofconversation conversation, " +
    "openfire.ofconparticipant participant " +
    "WHERE conversation.conversationID = participant.conversationID " +
    "AND participant.bareJID LIKE ? " +
    "AND conversation.startDate between ? AND ?)";

但是，当以以下方式提取列表的内容时：

for (Conversation conversation : conversations) {
builder.append(conversation.getId());
            builder.append(",");
            builder.append(conversation.getRoom());
            builder.append(",");
            builder.append(conversation.getIsExternal());
            builder.append(",");
            builder.append(conversation.getStartDate());            
            builder.append(",");            
            builder.append(conversation.getEndDate());
            builder.append(",");  
            builder.append(conversation.getMsgCount());
            out.write(builder.toString()); 
}

我收到一个错误：

java.util.LinkedHashMap cannot be cast to net.org.messagehistory.model.Conversation

如何将这个linkedMap转换为所需的对象？

谢谢

Answer 1

为了将查询的结果集映射到特定的Java类，最好使用RowMapper将结果集中的列转换为对象实例（假设您对在其他地方使用该对象感兴趣）。

有关如何使用行映射器的信息，请参见第12.2.1.1节“使用JDBC进行数据访问”。

简而言之，您将需要以下内容：

List<Conversation> actors = jdbcTemplate.query(
    SELECT_ALL_CONVERSATIONS_SQL_FULL,
    new Object[] {userId, dateFrom, dateTo},
    new RowMapper<Conversation>() {
        public Conversation mapRow(ResultSet rs, int rowNum) throws SQLException {
            Conversation c = new Conversation();
            c.setId(rs.getLong(1));
            c.setRoom(rs.getString(2));
            [...]
            return c;
        }
    });