jdbcTemplate.queryForList的返回类型（sql，object，classType） [英] Return Type for jdbcTemplate.queryForList(sql, object, classType)

问题描述

我正在使用jdbcTemplate.queryForList以下列方式执行命名查询：

I'm executing a named query using jdbcTemplate.queryForList in the following manner:

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

SQL查询是：

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 ?)";

但是当按以下方式提取列表内容时：

But when extracting the content of the list in the following manner:

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()); 
}

我收到错误消息：

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

如何将此LinkedMap转换为所需的对象??

How do I convert this linkedMap into the desired Object??

谢谢

推荐答案

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

In order to map a the result set of query to a particular Java class you'll probably be best (assuming you're interested in using the object elsewhere) of with a RowMapper to convert the columns in the result set into an object instance.

参见使用JDBC进行数据访问的第12.2.1.1节。

See Section 12.2.1.1 of Data access with JDBC on how to use a row mapper.

简而言之，你'我需要这样的东西：

In short, you'll need something like:

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;
        }
    });

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