package jef.database.query;
import java.util.ArrayList;
import java.util.List;
import jef.database.Condition;
import jef.database.Condition.Operator;
import jef.database.DbFunction;
import jef.database.DbUtils;
import jef.database.Field;
import jef.database.dialect.DatabaseDialect;
import jef.database.dialect.type.ColumnMapping;
import jef.database.meta.ITableMetadata;
import jef.database.wrapper.clause.HavingEle;
public final class SelectColumn extends SingleColumnSelect{
private String populateTo;//拼装路径，默认应该和alias一致
private String alias;
private Field targetField;
private ITableMetadata meta;
protected List<DbFunctionCall> func; //附加的函数
//缓存一个不带别名的列，以提高速度
private String columnSimpleName;//不带别名的参数
/**
* 转换为Having子句
*/
public HavingEle toHavingClause(DatabaseDialect profile,String tableAlias,SqlContext context){
HavingEle h=new HavingEle();
String column=innerGetColumn(profile, tableAlias);
h.column=column;
h.sql=Condition.toSql(column, havingCondOperator, havingCondValue, profile, null, null);
h.havingCondOperator=this.havingCondOperator;
h.havingCondValue=this.havingCondValue;
return h;
}
/**
* 设置having子句条件
* @param oper
* @param value
* @return
*/
public SelectColumn having(Operator oper,Object value){
this.projection=projection| PROJECTION_HAVING;
this.havingCondOperator=oper;
this.havingCondValue=value;
return this;
}
/**
* 设置having子句条件（该表达式不作为被选择列）。默认情况下 .column().sum().having(">",100);时， column().sum()也会作为查询列之一被查出。
* 使用havingOnly方法添加的having则是纯作为条件，不会作为查询列。
*
* @param oper
* @param value
* @return
*/
public SelectColumn havingOnly(Operator oper,Object value){
this.projection=projection |PROJECTION_HAVING_NOT_SELECT;
this.havingCondOperator=oper;
this.havingCondValue=value;
return this;
}
/**
* count(xxx)
* @return
*/
public SelectColumn count(){
this.projection=PROJECTION_COUNT;
return this;
}
/**
* 求和
* @return
*/
public SelectColumn sum(){
this.projection=PROJECTION_SUM;
return this;
}
/**
* 求平均数
* @return
*/
public SelectColumn avg(){
this.projection=PROJECTION_AVG;
return this;
}
/**
* 取最大值
* @return
*/
public SelectColumn max(){
this.projection=PROJECTION_MAX;
return this;
}
/**
* 取最小值
* @return
*/
public SelectColumn min(){
this.projection=PROJECTION_MIN;
return this;
}
/**
* 对应count(distinct xx)
* @return
*/
public SelectColumn countDistinct(){
this.projection=PROJECTION_COUNT_DISTINCT;
return this;
}
/**
* 指定按照此列进行 group by操作，同时选出此列
* @return
*/
public SelectColumn group() {
this.projection=PROJECTION_GROUP;
return this;
}
/**
* 指定按此列进行函数计算
* @param func
* @param params
* @return
*/
public SelectColumn funcTemplate(String func,String... params){
this.projection=PROJECTION_CUST_FUNC;
if(this.func==null){
this.func=new ArrayList<DbFunctionCall>();
}
this.func.add(new DbFunctionCall(func,params));
return this;
}
/**
* 指定按此列进行函数计算
* @param func
* @param params
* @return
*/
public SelectColumn func(DbFunction func,String... params){
this.projection=PROJECTION_CUST_FUNC;
if(this.func==null){
this.func=new ArrayList<DbFunctionCall>();
}
this.func.add(new DbFunctionCall(func,params));
return this;
}
SelectColumn(Field field,String populateTo){
this.targetField=field;
if(populateTo==null)populateTo=field.name();
this.populateTo=populateTo;
this.meta=DbUtils.getTableMeta(field);
}
void setProjection(int projection) {
this.projection = projection;
}
/**
* 将Projection重置
*/
public void clearProjection(){
this.projection=PROJECTION_NORMAL;
this.func=null;
}
/**
* 指定别名。这个方法不仅仅指定该查询列的别名，还指定该列将写入到指定对象字段中去
* @param alias
* @return
*/
public SelectColumn as(String alias) {
this.alias = alias;
if(alias!=null){
this.populateTo=alias;
}
return this;
}
public SelectColumn toField(String property){
this.populateTo=property;
return this;
}
public String getName() {
return populateTo;
}
// 生成选择语句时生成列名别，null表示无别名
public String getSelectedAlias(String tableAlias,DatabaseDialect profile) {
return DbUtils.escapeColumn(profile,profile.getObjectNameToUse(alias));
}
@Override
public String getResultAlias(String tableAlias, DatabaseDialect profile) {
if(alias==null){
if(columnSimpleName==null){
throw new IllegalArgumentException();
}
return columnSimpleName.toUpperCase();
}else{
return alias.toUpperCase();
}
}
private String innerGetColumn(DatabaseDialect profile,String tableAlias){
//因为第一次操作列名改为额大写，造成第二次Parse出错
columnSimpleName=DbUtils.toColumnName(targetField, profile,null);//不带别名的列名
String name= DbUtils.toColumnName(targetField, profile,tableAlias);
int key=projection & 0xFF;
if(key>0){
// if(StringUtils.isEmpty(alias)){//强行取Alias(无必要)
// alias="C".concat(RandomStringUtils.randomAlphanumeric(12));
// }
switch(key){
case PROJECTION_COUNT:
return "count(".concat(name).concat(")");
case PROJECTION_COUNT_DISTINCT:
return "count(distinct ".concat(name).concat(")");
case PROJECTION_SUM:
return "sum(".concat(name).concat(")");
case PROJECTION_AVG:
return "avg(".concat(name).concat(")");
case PROJECTION_MAX:
return "max(".concat(name).concat(")");
case PROJECTION_MIN:
return "min(".concat(name).concat(")");
case PROJECTION_CUST_FUNC:
String start=name;
for(DbFunctionCall func:this.func){
Object[] args;
if(func.getVarIndex()==-1){
args=new String[]{start};
}else{
args=func.getArgs();
args[func.getVarIndex()]=start;
}
if(func.getFunc()==null){
StringBuilder sb=new StringBuilder(func.getName()).append('(');
for(int i=0;i<args.length;i++){
if(i>0){
sb.append(", ");
}
sb.append(args[i]);
}
start=sb.append(')').toString();
}else{
start=profile.getFunction(func.getFunc(),args);
}
}
return start;
default:
throw new IllegalArgumentException("Unknown projection "+ key);
}
}else{
return name;
}
}
//当生成选择语句时计算列名称
public String getSelectItem(DatabaseDialect profile,String tableAlias,SqlContext context) {
if(targetField==null)return null;
if((projection & PROJECTION_HAVING_NOT_SELECT)>0){
return null;//纯having的列，不进行select,也不进行group
}
if(targetField instanceof JpqlExpression){
return columnSimpleName=((JpqlExpression) targetField).toSqlAndBindAttribs(context, profile);
}
return innerGetColumn(profile,tableAlias);
}
public boolean isSingleColumn() {
return true;
}
public ColumnMapping getTargetColumnType() {
return meta.getColumnDef(targetField);
}
@Override
public String toString() {
return populateTo+":"+targetField+(alias==null?"":" as "+alias);
}
}