sql语句实现的具体过程_set a strategy for handling the query results. thi-优快云博客

本文介绍了一种在Java项目中使用SQL查询结合Hibernate进行结果转换的方法。具体展示了如何通过字符串构建SQL语句并利用Hibernate的API执行查询，再通过设置结果转换器将查询结果转化为Map集合。

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一般我们将sql语句的具体实现放在service/impl下的xxxServiceImpl中，
最好加上在方法开头加上@Override，@Override表示对父类方法的重写，
写上还可以避免方法名和参数写错。
代码如下:

    @Override
    // 稿件统计-获取入库稿件列表
    public List<Map<String, Object>> bankScriptList(Integer roleId, Integer type, Integer num) throws ParseException {
        String bTime = TimeUtils.getByType(type, num);
        String eTime = TimeUtils.getByType(4, num);

        List<Map<String, Object>> list1 = new ArrayList<>();
        String aString = "select distinct(sp.script_origin_id),sp.module_id from script_process as sp left join script_module as sm on sp.script_origin_id =sm.script_origin_id where sp.user_id IN ("
                + "" + com.util.StringUtils.convertListToString(userIdList(departmentIdList(roleId))) + ")"
                + " and sp.isdelete = 0 and sm.isdelete = 0 and sm.script_status_id in (19,20) AND sm.update_time > '"
                + bTime + "' AND sm.update_time < '" + eTime + "'";
        Query query = this.dao.getSession().createSQLQuery(aString);
        query.setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);
        list1 = query.list();
        return list1;
    }

bTime、eTime是我自己在TimeUtils定义的开始时间和结束时间，
将sql语句写在aString字符串中，
然后用dao.getSession().createSQLQuery(aString)方法执行对aString
语句的查询，再通过query.setResultTransformer()将query的结果转化为map，
然后将query的结果转化为list返回，即将map放到list中返回。
    query.setResultTransformer（）的代码如下:

    /**
     * Set a strategy for handling the query results. This can be used to change
     * "shape" of the query result.
     *
     * @param transformer The transformer to apply
     * @return this (for method chaining)
     */
    public Query setResultTransformer(ResultTransformer transformer);

Transformers的代码如下:

package org.hibernate.transform;


final public class Transformers {

    private Transformers() {}

    /**
     * Each row of results is a <tt>Map</tt> from alias to values/entities
     */
    public static final AliasToEntityMapResultTransformer ALIAS_TO_ENTITY_MAP =
            AliasToEntityMapResultTransformer.INSTANCE;

    /**
     * Each row of results is a <tt>List</tt> 
     */
    public static final ToListResultTransformer TO_LIST = ToListResultTransformer.INSTANCE;

    /**
     * Creates a resulttransformer that will inject aliased values into 
     * instances of Class via property methods or fields.
     */
    public static ResultTransformer aliasToBean(Class target) {
        return new AliasToBeanResultTransformer(target);
    }

}

然后我们需要在service/impl下的xxxService中写上一句来注明这个方法：
public List<Map<String, Object>> bankScriptList(Integer roleId, Integer type, Integer num) throws ParseException;
之后我们就可以在xxxController中调用这个sql语句的查询方法，比如：

    List<Map<String, Object>> lists = userWorkStaticsService.bankScriptList(roleId, type, num);
    List<Map<String, Object>> list1 = new ArrayList<Map<String, Object>>();
    //然后用for（）方法遍历lists中的map对象
    for (Map<String, Object> map : lists) {
        //新建map1，将查询结果put到map1中；
        Map<String, Object> map1 = new HashMap<>();
        map1.put("draftNum", map.get("draftNum"));
        map1.put("processingNum", map.get("processingNum"));
        map1.put("waitPublishNum", map.get("waitPublishNum"));
        map1.put("waitCheckNum", map.get("waitCheckNum"));
        list1.add(map1);
    }

然后将上面的list1返给前端，让前端解析出结果显示出来就可以了。