在hibernate框架中,常規查詢方法是:

        Configuration configuration = new Configuration();
        configuration.configure();
        Session session = configuration.buildSessionFactory().getCurrentSession();
        Transaction transaction = session.beginTransaction();
        Query query = session.createQuery
 
("from Studnet where sid=:sid");
        query.setParameter("sid", 1L);
        List<Student> students = query.list();
        for (Student student : students) {
            //得到Student物件
            System.out.println(student.getName());
        }
        transaction.commit();
    }

但是在專案中,查詢條件往往有很多,某些查詢條件也不能確定,如果使用上面的方法,那麼就要寫大量基本重複的查詢方法.為了簡化工作量,封裝了一種通用的查詢方法,將查詢條件封裝到一個Map＜String, Object＞集合中, 動態的生成查詢語句傳送給資料庫得到查詢結果

下面這個是查詢表或者物件封裝的方法．

import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class QueryTable {

    SessionFactory sessionFactory;

    {
        Configuration configuration = new
 
 Configuration();
        configuration.configure();
        sessionFactory = configuration.buildSessionFactory();
    }

    /**
     * 單表單條記錄查詢
     * @param clazz
     * @param varables
     * @return
     */
    public <T> T querySingleResult(Class<T> clazz, Map<String, Object> varables){
        Session session = sessionFactory.getCurrentSession();
        Transaction transaction = session.beginTransaction();
        Query query = selectStatement(clazz, varables, session);
        return (T) query.uniqueResult();
    }

    /**
     * 單表多條記錄查詢
     * @param className 要查詢的物件
     * @param varables 封裝查詢條件的map
     * @return 返回查詢結果的List集合
     */
    public <T> List<T> queryResultList(Class<T> className, Map<String,Object> varables){        
        Session session = sessionFactory.getCurrentSession();
        Transaction transaction = session.beginTransaction();               
        List<T> valueList = selectStatement(className, varables, session).list();
        transaction.commit();
        return valueList;       
    }

    /**
     * 拼接SQL查詢字串,得到Query並賦值查詢條件
     * @param className
     * @param varables
     * @param session
     * @return Query
     */
    private <T> Query selectStatement(Class<T> className, Map<String,Object> varables, Session session) {
        StringBuilder stringBuilder = new StringBuilder();
        /*
         * 通過className得到該實體類的字串形式,
         */
        stringBuilder.append("from " + sessionFactory.getClassMetadata(className).getEntityName());
        stringBuilder.append(" where 1=1 ");
        /*
         * 動態的拼接sql語句,如果一個屬性的值為"", 則不往條件中新增.
         */
        for(Entry<String, Object> entry : varables.entrySet()){
            if(!entry.getValue().equals("")){
                stringBuilder.append(" and " + entry.getKey()+"=:" + entry.getKey());
            }
        }

        Query query = session.createQuery(stringBuilder.toString());
        /*
         * 動態的給條件賦值
         */
        for(Entry<String, Object> entry : varables.entrySet()){
            if(!entry.getValue().equals("")){
                query.setParameter(entry.getKey(), entry.getValue());
            }
        }
        return query;
    }


}

上面一共提供了兩個方法，一個返回單個結果，一個返回多個結果，Ｄｅｍｏ如下：

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.junit.Test;

import com.ruinan.domain.Course;
import com.ruinan.domain.Student;

public class testQueryTable {

    QueryTable queryTable = new QueryTable();
    /**
     * 多個結果查詢
     * @throws InstantiationException
     * @throws IllegalAccessException
     */
    @Test
    public void testQueryResultList() throws InstantiationException, IllegalAccessException {
        /*
         * 將查詢條件封裝到map中.
         * 例 description=www
         */
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("description", "www");

//      List<Student> students = queryClass(Student.class, map);
//      for (Student student : students) {
//          System.out.println(student.getName()+ "/" + student.getDescription());
//      }
        /*
         * 得到查詢結果,是一個List集合
         */
        List<Course> courses = queryTable.queryResultList(Course.class, map);
        for (Course course : courses) {
            System.out.println(course.getName());
        }
    }

    /**
     * 查詢單個結果
     */
    @Test
    public void testQuerySingleResult() {
        /*
         * 將查詢條件封裝到map中.
         * 例 description=www
         */
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("sid", 3L);
        /*
         * 得到查詢結果
         */
        Student student = queryTable.querySingleResult(Student.class, map);
        System.out.println(student.getDescription());
    }
}