QueryHelper插件类(hql)详解编程语言

package cn.itcast.core.util; 
 
import java.util.ArrayList; 
import java.util.List; 
 
public class QueryHelper { 
     
    //from子句 
    private String fromClause = ""; 
    //where子句 
    private String whereClause = ""; 
    //order by子句 
    private String orderByClause = ""; 
     
    private List<Object> parameters; 
    //排序递次 
    public static String ORDER_BY_DESC = "DESC";//降序 
    public static String ORDER_BY_ASC = "ASC";//升序 
     
    /** 
     * 组织from 子句 
     * @param clazz 实体类 
     * @param alias 实体类对应的别号 
     */ 
    public QueryHelper(Class clazz, String alias){ 
        fromClause = "FROM " + clazz.getSimpleName() + " " + alias; 
    } 
     
    /** 
     * 组织where子句 
     * @param condition 查询前提语句；例如：i.title like ? 
     * @param params 查询前提语句中?对应的查询前提值；例如： %题目% 
     */ 
    public void addCondition(String condition, Object... params){ 
        if (whereClause.length() > 1) {//非第一个查询前提 
            whereClause += " AND " + condition; 
        } else {//第一个查询前提 
            whereClause += " WHERE " + condition; 
        } 
         
        //设置查询前提值到查询前提值鸠合中 
        if(parameters == null){ 
            parameters = new ArrayList<Object>(); 
        } 
        if(params != null){ 
            for(Object param: params){ 
                parameters.add(param); 
            } 
        } 
    } 
     
    /** 
     * 组织order by子句 
     * @param property 排序属性，如：i.createTime 
     * @param order 排序递次，如：DESC 或者 ASC 
     */ 
    public void addOrderByProperty(String property, String order){ 
        if (orderByClause.length() > 1) {//非第一个排序属性 
            orderByClause += "," + property + " " + order; 
        } else {//第一个排序属性 
            orderByClause = " ORDER BY " + property + " " + order; 
        } 
    } 
 
    //查询hql语句 
    public String getQueryListHql(){ 
        return fromClause + whereClause + orderByClause; 
    } 
     
    //查询统计数的hql语句 
    public String getQueryCountHql(){ 
        return "SELECT COUNT(*) " + fromClause + whereClause; 
    } 
     
    //查询hql语句中?对应的查询前提值鸠合 
    public List<Object> getParameters(){ 
        return parameters; 
    } 
}