如何使用JDBCTemplate.queryForMap获取Map数据 [英] How to get Map data using JDBCTemplate.queryForMap

问题描述

如何从 JDBCTemplate.queryForMap（）加载数据并返回Map接口。如何在map内部维护查询数据。我试图加载但是我得到了低于异常，即 org.springframework.dao.IncorrectResultSizeDataAccessException：结果不正确

How to load data from JDBCTemplate.queryForMap() and it returns the Map Interface.How the maintained the query data internally in map.I trying to load but i got below exception i.e., org.springframework.dao.IncorrectResultSizeDataAccessException: Incorrect result

代码： -

public List getUserInfoByAlll() {
    List profilelist=new ArrayList();
    Map m=new HashMap();
    m=this.jdbctemplate.queryForMap("SELECT userid,username  FROM USER");
    Set s=m.keySet();
    Iterator it=s.iterator();
    while(it.hasNext()){
        String its=(String)it.next();
        Object ob=(Object)m.get(its);
        log.info("UserDAOImpl::getUserListSize()"+ob);
    }
    return profilelist;
}

Plz帮帮我

推荐答案

queryForMap 是合适的。你选择没有 where 子句，所以你可能想要 queryForList 。该错误可能表明 queryForMap 需要一行，但您查询的是检索多行。

queryForMap is appropriate if you want to get a single row. You are selecting without a where clause, so you probably want to queryForList. The error is probably indicative of the fact that queryForMap wants one row, but you query is retrieving many rows.

查看文档。 queryForList 只需要sql;返回类型是

Check out the docs. There is a queryForList that takes just sql; the return type is a

列表< Map< String，Object>> 。

所以一旦你得到了结果，你就可以做你正在做的事情。我会做类似的事情

So once you have the results, you can do what you are doing. I would do something like

List results = template.queryForList(sql);

for (Map m : results){
   m.get('userid');
   m.get('username');
} 

我会让你填写细节，但我不会迭代在这种情况下的键。我喜欢明确我期待的内容。

I'll let you fill in the details, but I would not iterate over keys in this case. I like to explicit about what I am expecting.

如果你有一个用户对象，你真的想要加载用户实例，你可以使用 queryForList 来获取sql和类类型

If you have a User object, and you actually want to load User instances, you can use the queryForList that takes sql and a class type

queryForList（String sql，Class< T> elementType）

（自从我离开Javaland以来，Spring已经发生了很大变化。）

(wow Spring has changed a lot since I left Javaland.)

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