/*
* This file is part of Zql.
*
* Zql is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Zql is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Zql. If not, see <http://www.gnu.org/licenses/>.
*/
package org.gibello.zql.sample.api;
import java.sql.SQLException;
import java.util.Vector;
import java.util.Hashtable;
import java.util.Enumeration;
import java.io.*;
import org.gibello.zql.*;
/**
* <pre>
* </pre>
*/
public class PreparedDemo {
public static void main(String args[]) {
try {
ZqlParser p = null;
if(args.length < 1) {
System.out.println("Reading SQL from stdin (quit; or exit; to quit)");
p = new ZqlParser(System.in);
} else {
p = new ZqlParser(new DataInputStream(new FileInputStream(args[0])));
}
// Read all SQL statements from input
ZStatement st;
while((st = p.readStatement()) != null) {
System.out.println(st.toString()); // Display the statement
if(st instanceof ZQuery) { // An SQL query: query the DB
handleQuery((ZQuery)st);
} else if(st instanceof ZInsert) { // An SQL insert
handleInsert((ZInsert)st);
} else if(st instanceof ZUpdate) {
handleUpdate((ZUpdate)st);
} else if(st instanceof ZDelete) {
handleDelete((ZDelete)st);
}
}
} catch(Exception e) {
e.printStackTrace();
}
}
/**
*/
static void handleQuery(ZQuery q) throws Exception {
System.out.println("SELECT Statement:");
Vector sel = q.getSelect(); // SELECT part of the query
ZExpression w = (ZExpression)q.getWhere();
if(w != null) {
Hashtable meta = null;
Vector from = q.getFrom(); // FROM part of the query
// Column metadata: Hashtable (alias, table name)
// Will be used by handleWhere() to resolve aliases into table names
meta = new Hashtable();
for(int i=0; i<from.size(); i++) {
ZFromItem fi = (ZFromItem)from.elementAt(i);
String alias = fi.getAlias();
if(alias == null) alias = fi.getTable();
meta.put(alias.toUpperCase(), fi.getTable());
}
handleWhere(w, meta);
}
}
static void handleInsert(ZInsert ins) throws Exception {
System.out.println("INSERT Statement:");
String tab = ins.getTable();
Vector values = ins.getValues();
if(values == null) {
System.out.println("no VALUES(), probably a subquery ?");
}
int nval = values.size();
Vector columns = ins.getColumns();
if(columns == null) {
System.out.println("no column names, assuming _col_1"
+ (nval > 1 ? " to _col_" + nval : ""));
columns = new Vector(nval);
for(int i=1; i<=nval; i++) {
columns.addElement("_col_" + i);
}
}
for (int i=0; i<nval; i++) {
ZExp v = (ZExp)values.elementAt(i);
if(isPreparedColumn(v)) {
System.out.println("[" + tab + "," + columns.elementAt(i) + "]");
}
}
}
static void handleUpdate(ZUpdate upd) throws Exception {
System.out.println("UPDATE Statement:");
String tab = upd.getTable();
Hashtable set = upd.getSet();
Enumeration k = set.keys();
while(k.hasMoreElements()) {
String col = (String)k.nextElement();
ZExp e = (ZExp)set.get(col);
if(isPreparedColumn(e)) {
System.out.println("[" + tab + "," + col + "]");
}
}
ZExpression w = (ZExpression)upd.getWhere();
if(w != null) {
Hashtable meta = new Hashtable(1);
meta.put(tab, tab);
handleWhere(w, meta);
}
}
static void handleDelete(ZDelete del) throws Exception {
System.out.println("DELETE Statement:");
String tab = del.getTable();
ZExpression w = (ZExpression)del.getWhere();
if(w != null) {
Hashtable meta = new Hashtable(1);
meta.put(tab, tab);
handleWhere(w, meta);
}
}
static void handleWhere(ZExp e, Hashtable meta) throws Exception {
//if(meta != null) System.out.println(meta);
if(! (e instanceof ZExpression)) return;
ZExpression w = (ZExpression)e;
Vector operands = w.getOperands();
if(operands == null) return;
// Look for prepared column ("?")
String prepared = null;
for(int i=0; i<operands.size(); i++) {
if(isPreparedColumn((ZExp)operands.elementAt(i))) {
prepared = ((ZConstant)operands.elementAt(0)).getValue();
if(operands.size() != 2) {
throw new Exception("ERROR in where clause ?? found:"
+ w.toString());
}
break;
}
}
if(prepared != null) { // prepared contains the (raw) column or alias name
boolean noalias = false;
// Parse raw column name to look for table name & columnalias name
// Syntax: [[schema].table.]columnalias
String tbl = null;
int pos = prepared.lastIndexOf('.');
if(pos > 0) { // [schema.]table.columnalias
tbl = prepared.substring(0, pos);
prepared = prepared.substring(pos+1); // The real column name
if((pos = tbl.lastIndexOf('.')) > 0) { // schema.table.columnalias
tbl = tbl.substring(pos+1);
noalias = true;
}
}
// Now tbl is the table name or null, prepared is the column name
// Note tbl may be an alias
// (like in "select * from mytable t where t.mykey=1", the table name is
// "mytable", not "t")
if(! noalias) {
// If tbl is an alias, resolve it
if(tbl != null) tbl = (String)meta.get(tbl.toUpperCase());
}
if(tbl == null && meta.size() == 1) {
Enumeration keys = meta.keys();
tbl = (String)keys.nextElement();
}
// Now tbl is either the real table name, or null if unresolved
System.out.println("[" + (tbl == null ? "unknown" : tbl) + ","
+ prepared + "]");
} else { // No prepared column, go further analyzing the expression
for(int i=0; i<operands.size(); i++) {
handleWhere(w.getOperand(i), meta); // WARNING - Recursive call...
}
}
}
static boolean isPreparedColumn(ZExp v) {
return
(v instanceof ZExpression && ((ZExpression)v).getOperator().equals("?"));
}
};
