Hibernate的sql语句，HQL写法。你应该知道的

最近刚进入项目，好多都不太熟悉，而且公司的项目框架大部分都是SSH。由于之前接触的大部分是SSM，所以好多也需要自己去学习。

没多长时间，上面就给我安排了一个追加功能，那就是对所有信息的一个统计--求平均值、总和。他们的写法是这样的。好多都是HQL写法，对这个不是很了解。自己也都是边做边学。

Finder f = Finder.create("from ChannelTrade a ");
            String where = " where ";
            if (channelTradeForm.getTradeNo() != null && channelTradeForm.getTradeNo().length() > 0) {
                f.append(where + " a.tradeNo like :tradeNo").setParam("tradeNo", "%" + channelTradeForm.getTradeNo() + "%");
                where = " and ";
            }
            if(channelTradeForm.getCrsNo()!= null && channelTradeForm.getCrsNo().length()>0){
                f.append(where + " a.crsNo like :crsNo").setParam("crsNo", "%"+ channelTradeForm.getCrsNo()+"%");
                where = " and ";
            }

            if (channelTradeForm.getHotel() != null && !StringUtils.isEmpty(channelTradeForm.getHotel().getCode()) && !StringUtils.isEmpty(channelTradeForm.getHotel().getName())) {
                f.append(where + " a.hotel.code = :hotelCode").setParam("hotelCode", channelTradeForm.getHotel().getCode());
                where = " and";
            }

            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            if (channelTradeForm.getArrDateStart() != null && channelTradeForm.getArrDateStart().length()>0 && channelTradeForm.getArrDateEnd() != null && channelTradeForm.getArrDateEnd().length()>0) {
                f.append(where + " a.arrDate >= :arrDateStart").setParam("arrDateStart", sdf.parse(channelTradeForm.getArrDateStart()));
                where = " and";
                f.append(where + " a.arrDate <= :arrDateEnd").setParam("arrDateEnd", sdf.parse(channelTradeForm.getArrDateEnd()));
                where = " and";
            }
            if (channelTradeForm.getDepDateStart() != null && channelTradeForm.getDepDateStart().length()>0 && channelTradeForm.getDepDateEnd() != null && channelTradeForm.getDepDateEnd().length()>0) {
                f.append(where + " a.depDate >= :depDateStart").setParam("depDateStart", sdf.parse(channelTradeForm.getDepDateStart()));
                where = " and";
                f.append(where + " a.depDate <= :depDateEnd").setParam("depDateEnd", sdf.parse(channelTradeForm.getDepDateEnd()));
                where = " and";
            }

            f.append(" order by a.createDatetime desc");
            return find(f, channelTradeForm.getPageNo(), channelTradeForm.getPageSize());

这个HQL写法是用Finder封装好了的，基本上不用你去怎么写sql语句，为了更好的知道这个FInder里面都封装了那些方法，你可以点进去查看一下，是这样了。

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.kaiyuan.common.hibernate4;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.type.Type;

public class Finder {
    private StringBuilder hqlBuilder;
    private List<String> params;
    private List<Object> values;
    private List<Type> types;
    private List<String> paramsList;
    private List<Collection<Object>> valuesList;
    private List<Type> typesList;
    private List<String> paramsArray;
    private List<Object[]> valuesArray;
    private List<Type> typesArray;
    private int firstResult = 0;
    private int maxResults = 0;
    public static final String ROW_COUNT = "select count(*) ";
    public static final String FROM = "from";
    public static final String DISTINCT = "distinct";
    public static final String HQL_FETCH = "fetch";
    public static final String ORDER_BY = "order";
    public static final String GROUP_BY = "group";

    protected Finder() {
    }

    public Finder(String hql) {
        this.hqlBuilder = new StringBuilder(hql);
    }

    public static Finder create(String hql) {
        Finder finder = new Finder(hql);
        return finder;
    }

    public Finder append(String hql) {
        this.hqlBuilder.append(hql);
        return this;
    }

    public String getOrigHql() {
        return this.hqlBuilder.toString();
    }

    public String getRowCountHql() {
        String hql = this.hqlBuilder.toString();
        int fromIndex = hql.toLowerCase().indexOf("from");
        String projectionHql = hql.substring(0, fromIndex);
        hql = hql.substring(fromIndex);
        String rowCountHql = hql.replace("fetch", "");
        int index = rowCountHql.indexOf("order");
        if (index > 0) {
            rowCountHql = rowCountHql.substring(0, index);
        }

        hql = this.wrapProjection(projectionHql) + rowCountHql;
        return hql;
    }

    public int getFirstResult() {
        return this.firstResult;
    }

    public void setFirstResult(int firstResult) {
        this.firstResult = firstResult;
    }

    public int getMaxResults() {
        return this.maxResults;
    }

    public void setMaxResults(int maxResults) {
        this.maxResults = maxResults;
    }

    public Finder setParam(String param, Object value) {
        return this.setParam(param, value, (Type)null);
    }

    public Finder setParam(String param, Object value, Type type) {
        this.getParams().add(param);
        this.getValues().add(value);
        this.getTypes().add(type);
        return this;
    }

    public Finder setParams(Map<String, Object> paramMap) {
        Iterator var3 = paramMap.entrySet().iterator();

        while(var3.hasNext()) {
            Entry entry = (Entry)var3.next();
            this.setParam((String)entry.getKey(), entry.getValue());
        }

        return this;
    }

    public Finder setParamList(String name, Collection<Object> vals, Type type) {
        this.getParamsList().add(name);
        this.getValuesList().add(vals);
        this.getTypesList().add(type);
        return this;
    }

    public Finder setParamList(String name, Collection<Object> vals) {
        return this.setParamList(name, (Collection)vals, (Type)null);
    }

    public Finder setParamList(String name, Object[] vals, Type type) {
        this.getParamsArray().add(name);
        this.getValuesArray().add(vals);
        this.getTypesArray().add(type);
        return this;
    }

    public Finder setParamList(String name, Object[] vals) {
        return this.setParamList(name, (Object[])vals, (Type)null);
    }

    public Query setParamsToQuery(Query query) {
        int i;
        if (this.params != null) {
            for(i = 0; i < this.params.size(); ++i) {
                if (this.types.get(i) == null) {
                    query.setParameter((String)this.params.get(i), this.values.get(i));
                } else {
                    query.setParameter((String)this.params.get(i), this.values.get(i), (Type)this.types.get(i));
                }
            }
        }

        if (this.paramsList != null) {
            for(i = 0; i < this.paramsList.size(); ++i) {
                if (this.typesList.get(i) == null) {
                    query.setParameterList((String)this.paramsList.get(i), (Collection)this.valuesList.get(i));
                } else {
                    query.setParameterList((String)this.paramsList.get(i), (Collection)this.valuesList.get(i), (Type)this.typesList.get(i));
                }
            }
        }

        if (this.paramsArray != null) {
            for(i = 0; i < this.paramsArray.size(); ++i) {
                if (this.typesArray.get(i) == null) {
                    query.setParameterList((String)this.paramsArray.get(i), (Object[])this.valuesArray.get(i));
                } else {
                    query.setParameterList((String)this.paramsArray.get(i), (Object[])this.valuesArray.get(i), (Type)this.typesArray.get(i));
                }
            }
        }

        return query;
    }

    public Query createQuery(Session s) {
        return this.setParamsToQuery(s.createQuery(this.getOrigHql()));
    }

    private String wrapProjection(String projection) {
        return projection.indexOf("select") == -1 ? "select count(*) " : projection.replace("select", "select count(") + ") ";
    }

    private List<String> getParams() {
        if (this.params == null) {
            this.params = new ArrayList();
        }

        return this.params;
    }

    private List<Object> getValues() {
        if (this.values == null) {
            this.values = new ArrayList();
        }

        return this.values;
    }

    private List<Type> getTypes() {
        if (this.types == null) {
            this.types = new ArrayList();
        }

        return this.types;
    }

    private List<String> getParamsList() {
        if (this.paramsList == null) {
            this.paramsList = new ArrayList();
        }

        return this.paramsList;
    }

    private List<Collection<Object>> getValuesList() {
        if (this.valuesList == null) {
            this.valuesList = new ArrayList();
        }

        return this.valuesList;
    }

    private List<Type> getTypesList() {
        if (this.typesList == null) {
            this.typesList = new ArrayList();
        }

        return this.typesList;
    }

    private List<String> getParamsArray() {
        if (this.paramsArray == null) {
            this.paramsArray = new ArrayList();
        }

        return this.paramsArray;
    }

    private List<Object[]> getValuesArray() {
        if (this.valuesArray == null) {
            this.valuesArray = new ArrayList();
        }

        return this.valuesArray;
    }

    private List<Type> getTypesArray() {
        if (this.typesArray == null) {
            this.typesArray = new ArrayList();
        }

        return this.typesArray;
    }

    public static void main(String[] args) {
        Finder find = create("select distinct p FROM BookType join fetch p");
        System.out.println(find.getRowCountHql());
        System.out.println(find.getOrigHql());
    }
}

是不是感觉特别方便，里面有StringBuilder可以帮你去拼接（优势自己下去去百度哦）、distinct(去重)、fetch、order by（分组）。这样写确实有很多好处，比如你不用MyBatis在映射文件中写很复杂的sql语句了，Hibernate本来就是一个对象关系映射框架--ORM。而我现在也越来越对hibernate这种写法情有独钟，慢慢习惯这种写法带来的开心。不过，这种写法也有一定的局限性，比如在我进行统计的时候，我发现这样写根本就不正确

 String hql = "select new com.yyf.demo.pojo.ChannelTradeVo(c.hotel.name ," +
                    "sum(c.nights) ," +
                    "arrDate ," +
                    "depDate ," +
                    "(c.tradeAmount)/sum(c.nights) ," +
                    "sum(c.hotelTradeAmount) ," +
                    "sum(c.otherAmount))" +
                    "from ChannelTrade c where 1=1";

            Finder f = new Finder(hql);

项目运行的时候总是报错，也就是用HQl写法的时候，不能像SQL语句那样直接在语句中进行加减乘除

 String hql = "select new com.yyf.demo.pojo.ChannelTradeVo(c.hotel.name ," +
                    "sum(c.nights) ," +
                    "arrDate ," +
                    "depDate ," +
                    "(c.tradeAmount) ," +
                    "sum(c.hotelTradeAmount) ," +
                    "sum(c.otherAmount))" +
                    "from ChannelTrade c where 1=1";

            Finder f = new Finder(hql);

这样改过之后，并且，我直接在前台进行一个计算，也是可以的就可以正常运行。

其实，到这，我想说一句，程序员一定要熟悉业务，不然真的会走弯路，这都是我的前车之鉴。比如，交代我的任务是对所有酒店、间夜、平均房价、总收入进行统计报表，我以为这个平均房价是所有酒店的一个平均值，做出来之后，刚开始我们组长也没仔细看，没什么错就通过测试了，没过两天，我们组长就跟我说这个报表有问题，平均房价是房费收入和间夜量的平均值。通过这个教训让我吸取了不少教训。同时也让我深刻明白了对熟悉业务的高要求。