api.java

用JAVA实现的miniSQL

import java.io.*;

public class API {
    String reason;
    IndexManager indexmanager;
    RecordManager recordmanager;
    Catalog catalog;
    public API(IndexManager im, RecordManager rm, Catalog cl) {
    	indexmanager = im;
    	recordmanager = rm;
    	catalog = cl;
    }
    public boolean createTable(Interpreter cmd){
    	File table = new File(cmd.table);
    	if(table.exists()){
    		reason = new String("创建表的文件已存在");
    		return false;
    	}
    	try{
    		table.createNewFile();
    		RandomAccessFile rantable = new RandomAccessFile(table, "rw");
    		rantable.writeLong(0); //总的记录个数
    		rantable.writeLong(0); //块的个数
    		int rlenght=cmd.attnumber+1;
            for(int i=0;i<cmd.attnumber;i++)
        	    rlenght=rlenght+cmd.attlength[i];
        	if(rlenght < 9)
            	rlenght = 9;
    		rantable.writeInt(rlenght);//每个记录的长度
    		rantable.writeInt(4096/rlenght);//每个块多少个记录
    		rantable.writeLong(1024);//第一个空位置地址
    		rantable.close();
    	}catch(Exception e){
    		reason = new String("建立表文件失败");
    		return false;
    	}
    	    cmd.mean = 3;
    	    cmd.indexname = cmd.primarykey+"index";
    	    cmd.uniqueatt = cmd.primarykey;
    		return indexmanager.createIndex(cmd);
    }
    public boolean dropTable(Interpreter cmd){
    	File table = new File(cmd.table);
    	if(!table.exists()){
    		reason = new String("要删除的表不存在");
    		return false;
    	}
    	for(int i=0; i<cmd.attnumber; i++){
    		if(cmd.attindex[i]!=null){
    			new File(cmd.attindex[i]).delete();
    			recordmanager.deleteBlock(cmd.attindex[i]);
    		}
    	}
    	recordmanager.deleteBlock(cmd.table);
        return table.delete();
    }
    public boolean createIndex(Interpreter cmd){
    	return indexmanager.createIndex(cmd);
    }
    public boolean deleteIndex(Interpreter cmd){
    	File index = new File(cmd.indexname);
    	if(!index.exists()){
    		reason = new String("该索引的文件不存在");
    		return false;
    	}
    	recordmanager.deleteBlock(cmd.indexname);
    	return index.delete();
    }
    public boolean select(Interpreter cmd){
    	return recordmanager.getRecord(cmd);
    }
    public boolean insert(Interpreter cmd){
    	boolean a;
    	if(a=recordmanager.insertRecord(cmd))
    		catalog.addrecord(cmd.table);
    	return a;
    }
    public boolean delete(Interpreter cmd){
    	int a =recordmanager.deleteRecord(cmd);
    	long c;
    	if(a == -2){
    		c= catalog.gettablerecord(cmd.table);
    		catalog.deleteIndexfromTable(cmd.table);
    		for(int i=0; i<cmd.attnumber; i++)
    			if(cmd.attindex[i]!=null)
    		        catalog.deleteIndexfromTable(cmd.attindex[i]);
    		System.out.println("成功删除记录"+c+"项");
    		return true;
    	}
    	if(a>0){
            catalog.subrecord(cmd.table, a);
            System.out.println("成功删除记录"+a+"项");
            return true;
    	}
    	System.out.println("满足此删除条件的项不存在");
    	return true;
    }
    public boolean quit(Interpreter cmd){
    	return recordmanager.quit();
    }
    public boolean exefile(Interpreter cmd){
    	try{
    	BufferedReader exef = new BufferedReader(new FileReader(cmd.table)); 
    	String com;
    	com = exef.readLine();
    	String command = new String("");
    	while(com!=null){    		
    		int pos=0;
    		while(com!=null){
    			pos = com.indexOf(";");
    			if(pos>=0){
    				command = command+"\n"+com.substring(0,pos+1);
    				System.out.println(command.trim());
    				cmd.init(command);
    				if(catalog.test(cmd))
    					exec(cmd);
    				if(pos!=com.length()-1){
    					command = com.substring(pos,com.length());
    				}
    				else 
    				    command = new String("");
    				break;
    			}
    			command = command + "\n"+com;
    			com = exef.readLine();
    		}
    		com = exef.readLine();
    	}
    	exef.close();
    	}catch(Exception e){
    		System.out.println(e);
    	}
    	return true;
    }
    public boolean exec(Interpreter cmd){
    	switch(cmd.mean){
    		case 0:
    			return false;
    		case 1:{
    			if(createTable(cmd))
    				return true;
    			else{
    				System.out.println("API failed "+reason);
    				return false;
    			}
    				
    		}
    		case 2:{
    			if(dropTable(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 3:{
    			if(createIndex(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 4:{
    			if(deleteIndex(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 5:{
    			if(select(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 6:{
    			if(insert(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 7:{
    			if(delete(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 8:{
    			if(quit(cmd))
    				return true;
    			else
    				return false;
    		}
    		case 9:{
    			if(exefile(cmd))
    				return true;
    			else
    				return false;
    		}
    		default:
    			return false;
    	}
    }
}