stringmanager.java

一个简单的数据库

        }catch(Exception ex)
        {
            throw new OperationInfo("Select syntax error!The attribute(s) specified are not valid!");
        }
    }
    public static boolean isConditionExist(String cond)
    {
        if(cond.indexOf("=")!=-1||cond.indexOf("<>")!=-1||cond.indexOf("<")!=-1)
            return true;
        else if(cond.indexOf(">")!=-1||cond.indexOf(">")!=-1||cond.indexOf("<=")!=-1)
            return true;
        else if(cond.indexOf(">=")!=-1||cond.indexOf("between")!=-1||cond.indexOf("and")!=-1)
            return true;
        return false;
    }
    public static ArrayList<Tuple> operaSelect(String instr,StringBuilder builder,ArrayList<Integer>p) throws Exception
    {
        if(!verifySemicolon(instr))
            throw new OperationInfo("Select syntax error!Semicolon not satisfied!");
        instr=instr.substring(0,instr.indexOf(";"));
        int fromIndex;
        if((fromIndex=instr.indexOf("from"))==-1)
            throw new OperationInfo("Select syntax error:!No 'from' in this instruction!");
        String att=instr.substring(6,fromIndex).trim();
        if(att.length()==0)
            throw new OperationInfo("Select syntax error!:There must be some attributes names or '*'between 'select' and 'from'.");
        //////////////////////////////////////////////////////////
        boolean selectAll=false;
        int[] pos;
        String[] atts = null;
        ArrayList<String> attribs=getSelectAttribs(att);
        if(attribs==null)
            throw new OperationInfo("Select syntax error!");
        else if(attribs.get(0).equals("*"))
            selectAll=true;
        else
        {
            atts=new String[attribs.size()];
            for(int i=0;i<attribs.size();i++)
            {
                atts[i]=attribs.get(i);
            }
        }
        ///////////////////////////////////////////////////////////
        int whereIndex=instr.indexOf("where");
        boolean isCondExist=isConditionExist(instr);
        if(isCondExist&&whereIndex==-1)
            throw new OperationInfo("Select syntax error!No 'where' in this instruction!");
        if(!isCondExist&&whereIndex!=-1)
            throw new OperationInfo("Select syntax error!Conditions must be given.");
        String conditions=instr.substring(instr.indexOf("where")+5).trim();
        
        ///////////////////////////////////////////////////////////
        String tbName;
        if(whereIndex==-1)
            tbName=instr.substring(fromIndex+4).trim();
        else
            tbName=instr.substring(fromIndex+4,whereIndex).trim();
        if(!verifyName(tbName))
            throw new OperationInfo("Select syntax error!The table name:["+tbName+"] specified is not valid!");
        TableData tb=CatalogManager.getTableByName(tbName);
        
        if(tb==null)
            throw new OperationInfo("Select error!The table:["+tbName+"] doesn't exist!");
        if(selectAll)
        {
            atts=tb.getAttribNames();
            for(int i=0;i<atts.length;i++)
                p.add(i);
        }
        else
        {
            String[] namesTemp=tb.getAttribNames();
            pos=new int[atts.length];
            for(int i=0,k=0;i<atts.length;i++)
            {
                int j;
                for(j=0;j<namesTemp.length;j++)
                {
                    if(namesTemp[j].equals(atts[i]))
                    {
                        pos[k++]=j;
                        break;
                    }
                }
                if(j==namesTemp.length)
                    throw new OperationInfo("Select error!The attribte:["+atts[i]+"] specified doesn't exist!");
            }
            for(int i=0;i<pos.length;i++)
                p.add(pos[i]);
            /*StringBuilder sb=new StringBuilder();
            for(int i=0;i<p.size();i++)
                sb.append(p.get(i)+"\n");
            JOptionPane.showMessageDialog(null, sb.toString());
             */
        }
        builder.append(atts[0]);
        for(int i=1;i<atts.length;i++)
            builder.append(","+atts[i]);
       
        //无条件
        if(whereIndex==-1)
        {
            return APIManager.getAllTuplesForTable(tb); 
        }
        else    //有条件
        {
            Condition[] conds=getConditions(tb,conditions);
            return APIManager.getTuplesWithCondition(tb, conds);
        }
    }

    public static void operaDelete(String instr) throws Exception
    {
        //这个instr不包含";"
        if(!verifyBracket(instr))
            throw new OperationInfo("Delete syntax error!Brackets are not balanced!");
        int fromIndex=instr.indexOf("from");
        int whereIndex=instr.indexOf("where");
        
        if(fromIndex==-1)
            throw new OperationInfo("Delete syntax error!No 'from' in this instruction!");
        String temp=instr.substring(6,fromIndex).trim();
        if(temp.length()!=0)
            throw new OperationInfo("Delete syntax error!");
        boolean isCondExist=isConditionExist(instr);
        if(isCondExist&&whereIndex==-1)
            throw new OperationInfo("Delete syntax error!No 'where' in this instruction!");
        if(!isCondExist&&whereIndex!=-1)
            throw new OperationInfo("Delete syntax error!The conditions must be given!");
        
        String tbName;
        if(whereIndex==-1)
            tbName=instr.substring(fromIndex+4).trim();
        else
            tbName=instr.substring(fromIndex+4,whereIndex).trim();
        if(!verifyName(tbName))
            throw new OperationInfo("Delete syntax error!The table name specified:["+tbName+"]is not valid!");
        TableData tb=CatalogManager.getTableByName(tbName);
        if(tb==null)
            throw new OperationInfo("Select error!The table:["+tbName+"] doesn't exist!");
        
        if(whereIndex!=-1)
        {
            String conditions=instr.substring(instr.indexOf("where")+5).trim();
            Condition[] conds=getConditions(tb,conditions);
            APIManager.deleteTuplesWithCondition(tb,conds);
        }
        else
        {
            int delteNumber=APIManager.deleteAllTupleFromTable(tbName);
            if(delteNumber==0)
                throw new OperationInfo("The tuple(s) you want to delete doesn't exist!");
            else
                throw new Success("Delete successed!["+delteNumber+"]tuples have been successfully deleted!");      
        }
    }
    public static Condition[] getConditions(TableData tb,String cond) throws Exception
    {
        String[] attribNames=tb.getAttribNames();
        ArrayList<Condition> conditions=new ArrayList<Condition>();
        String[] conds=cond.split("and");
        int index;
        String name=null;
        String op=null;
        String value=null;
        
        int len=conds.length;
        for(int i=0;i<len;i++)
        {
            name=null;
            op=null;
            value=null;
            String temp=conds[i];
            Condition c=new Condition();
            
            if(temp.indexOf("<=")!=-1)
            {
                index=temp.indexOf("<=");
                name=temp.substring(0,index).trim();
                op="<=";
                value=temp.substring(index+2).trim();
            }
            else if(temp.indexOf(">=")!=-1)
            {
                index=temp.indexOf(">=");
                name=temp.substring(0,index).trim();
                op=">=";
                value=temp.substring(index+2).trim();
            }            
            else if(temp.indexOf("<>")!=-1)
            {
                index=temp.indexOf("<>");
                name=temp.substring(0,index).trim();
                op="<>";
                value=temp.substring(index+2).trim();
            }
            else if(temp.indexOf("<")!=-1)
            {
                index=temp.indexOf("<");
                name=temp.substring(0,index).trim();
                op="<";
                value=temp.substring(index+1).trim();
            }
            else if(temp.indexOf(">")!=-1)
            {
                index=temp.indexOf(">");
                name=temp.substring(0,index).trim();
                op=">";
                value=temp.substring(index+1).trim();
            }
            else if(temp.indexOf("=")!=-1)
            {
                index=temp.indexOf("=");
                name=temp.substring(0,index).trim();
                op="=";
                value=temp.substring(index+1).trim();
            }
            else 
                throw new OperationInfo("Select syntax error!The condition is not valid!");
            if(name==null||op==null||value==null)
                throw new OperationInfo("Select syntax error!The condition is not valid!");
            int j;
            for(j=0;j<attribNames.length;j++)
            {
                if(attribNames[j].equals(name))
                    break;
            }
            if(j==attribNames.length)
                throw new OperationInfo("Select error!The attribute name specified:["+name+"]doesn't exsit!"); 
            c.attribute=name;
            c.operand=op;
            c.compValue=value;
            conditions.add(c);
        }
        Condition[] cc=new Condition[conditions.size()];
        for(int i=0;i<conditions.size();i++)
        {
            cc[i]=conditions.get(i);
        }
        return cc;
    }
}