自定义公式生成伪SQL

由于小弟在文档编写能力上很不足，所以想通过学习一些别人的东西来提高一下，这个是我接手的一个模块，写出我认识到的文档，其他大家能批评指导。

需求：用户可以*录入公式，并根据公式计算出当前结果。
如公式为 指标test=#指标1+#指标2+同比增长(#指标3)
每天的batch时会根据不同日期进行计算指标test值，同时可能出现回算的情况。

分析：公式结构包括加减乘除，>=,<=,>,<,IF 判断和一些固定的计算方法(同比增长,环比增长等)，所有设计为在公式录入的时间，把公式转化为一个伪SQL的格式，同时在batch计算时替换掉固定位置的字符串，生成一个可以执行的SQL，最终执行的结果就是公式的计算结果。

设计：
指公式用到的符号分为3部分，+,-,*,/,>=,<=,>,<属于操作类符号；IF 判断和一些固定的计算方法(同比增长,环比增长等)属于方法类符号；#指标2等属于自定义符号；
操作类符号：统一定义接口Operator，所有的操作类符号都实现这个接口
Interface Operator {
//操作返回类型
public Type getReturnedType();
//支持的操作类型
public Type[] getSupportedInputType();
//操作符号
public String getWord();
}
方法类符号：统一定义接口Function,所有的方法类符号都实现这个接口
Interface Function {
public Type getReturnedType();
public Type[] getSupportedInputType();
public String getName();
//生成相就的SQL语句
public String toSql();
}
自定义符号:TakeHolder
Interface TakeHolder {
public type getReturnedType();
//自定义的符号的指定字符
public String getStart();
//判断是否有效
public boolean isValid(String token);
//转换
public String translate(String token);
}
定义一个Language用于指定当前模块所支持的操作符号，方法符号，自定义符号；
Interface Language {
public List getSupportedFunctions();
public List getSupportedOperators();
public List getSupportedTakeHolders();
//支持的类型
public List getSupportedTypes();
}
定义一个解析类，存储当前所支持的操作符号，方法符号，自定义符号,并解析用户录入的公式。
class TokenParse {
private HashMap operators = new HashMap();
private HashMap functions = new HashMap();
private HashMap holders = new HashMap();
public TokenParse(Language language) {
}
//解析公式
public List<Token> parse(String formula);
}
当用户输入的公式时，解析每一个字符，判断当前字符属于操作类符号，方法类符号，自定义符号；并存入到指定的token(type, exp)中,

public List<Token> parse(String exp) throws TokenException {
        // asert
        if (exp == null || exp.trim().length() == 0)
            return null;

        List<Token> tokens = new ArrayList<Token>();

        char[] chars = exp.toCharArray();
        StringBuffer sb = new StringBuffer();

        for (int i = 0; i < chars.length; i++) {
            char c = chars[i];
            if (isSeprator(c)) {
                String tmp = sb.toString();
                if (tmp.length() != 0) {
                    Token t = new Token(Token.EXPRESSION, tmp);
                    if (isOperand(tmp)) {
                        t.setType(Token.OPERAND);
                    }
                    tokens.add(t);

                }

                if (isSimpleOperator(c)) {
                    String op = "" + c;
                    Token top = new Token(Token.OPERATOR, op);
                    tokens.add(top);
                }

                sb = new StringBuffer();
                continue;
            }
            if (c == OPENED_BRACKET) {
                int count = 0;
                count++;
                sb.append(c);
                boolean colsed = false;
                for (i = i + 1; i < chars.length; i++) {
                    char jc = chars[i];
                    sb.append(jc);
                    if (jc == OPENED_BRACKET) {
                        count++;

                        continue;
                    }
                    if (c == DOUBLE_QUOTE) {

                        //sb.append(c);
                        boolean qcolsed = false;
                        for (i = i + 1; i < chars.length; i++) {
                            char qc = chars[i];
                            sb.append(qc);

                            if (qc == DOUBLE_QUOTE) {

                                qcolsed = true;

                                break;
                            }

                        }
                        if (!qcolsed)
                            throw new TokenException("双引号不匹配");
                        String tmp = sb.toString();
                        if (tmp.length() != 0) {
                            Token t = new Token(Token.OPERAND, tmp);
                            tokens.add(t);

                        }

                        sb = new StringBuffer();
                        continue;

                    }
                    if (jc == CLOSED_BRACKET) {
                        count--;
                        if (count == 0) {
                            colsed = true;
                            String tmp = sb.toString();
                            String name = tmp.substring(0, tmp
                                    .indexOf(OPENED_BRACKET));
                            if (name.length() == 0) {
                                Token t = new Token(Token.EXPRESSION, tmp);
                                tokens.add(t);

                            } else if (isFunctionName(name)) {
                                Token t = new Token(Token.FUNCTION, tmp);
                                tokens.add(t);

                            } else if (isOperator(name)) {
                                Token t = new Token(Token.OPERATOR, name);
                                tokens.add(t);

                                t = new Token(Token.EXPRESSION, tmp
                                        .substring(tmp.indexOf(OPENED_BRACKET)));
                                tokens.add(t);

                            } else {
                                throw new TokenException("不能识别的函数或操作符:" + name);
                            }
                            sb = new StringBuffer();

                            break;
                        }
                    }

                }
                if (!colsed)
                    throw new TokenException("括号不匹配");
                continue;
            }
           
            if (c == DOUBLE_QUOTE) {

                sb.append(c);
                boolean qcolsed = false;
                for (i = i + 1; i < chars.length; i++) {
                    char qc = chars[i];
                    sb.append(qc);

                    if (qc == DOUBLE_QUOTE) {

                        qcolsed = true;

                        break;
                    }

                }
                if (!qcolsed)
                    throw new TokenException("双引号不匹配");
                String tmp = sb.toString();
                if (tmp.length() != 0) {
                    Token t = new Token(Token.OPERAND, tmp);
                    tokens.add(t);

                }

                sb = new StringBuffer();
                continue;

            }
           
            sb.append(c);

        }
        String tmp = sb.toString();
        if (tmp.length() > 0) {
            Token t = new Token(Token.EXPRESSION, tmp);
            if (isOperand(tmp)) {
                t.setType(Token.OPERAND);
            }
            tokens.add(t);
        }
        if (tokens.size() == 1) {
            Token token = (Token) tokens.get(0);
            if (token.getType() == Token.EXPRESSION) {
                String tmpExp = token.getExp();
                if (tmpExp.charAt(0) == OPENED_BRACKET) {
                    String interal = tmpExp.substring(1, tmpExp.length() - 1);
                    return parse(interal);
                } else {
                    throw new TokenException("不能识别的操作数：" + tmpExp);
                }

            }
            if (token.getType() == Token.OPERATOR) {
                throw new TokenException("表达式尚未结束");
            }
        }
解析List<Token>，递归转化为一个Unit类
Class Unit {
public String operator = null;
public List oprands = new ArrayList();
public Type returnedType;
}
例：指标1+指标2转换的Unit为
Unit.operator = “+”;
Unit.oprands = {[指标1]，[指标2]}
Unit.returnedType = numeric;

public Unit compile(List tokens, TakeHolderContainer container)
            throws TokenException {
        Unit u = new Unit();
        Object[] ts = tokens.toArray();
        int length = ts.length;
        if (length == 1) {
            Token t = (Token) ts[0];
            if (t.getType() == Token.OPERATOR) {
                throw new TokenException("表达式没有结束，缺乏操作数");
            }
            if (t.getType() == Token.OPERAND) {
                doOperand(u, t, container);
            }
            if (t.getType() == Token.FUNCTION) {
                doFunction(u, t, container);
            }
            if (t.getType() == Token.EXPRESSION) {
                doExpression(u, t, container);
            }

            return u;
        }
        int top = findTopOperator(ts);
        if (top == -1) {
            throw new TokenException("表达式不完整");
        }
        // "Not" operator
        if (top == 0) {
            Token t = (Token) ts[0];
            u.operator = t.getExp();

            Object[] right = new Object[length - 1];
            System.arraycopy(ts, 1, right, 0, length - 1);
            List rl = Arrays.asList(right);

            Unit ru = this.compile(rl, container);
            String name = t.getExp().toUpperCase();
            Operator op = (Operator) name2Operator.get(name);
            if (op.getSupportedInputTypes()[0].getClass().isAssignableFrom(
                    ru.returnedType.getClass())) {
                u.oprands.add(ru);

                u.ref = op;
                u.returnedType = op.getReturnedType();
                u.type = Unit.OPERATION;
            } else {
                throw new TokenException("t.getExp().toUpperCase()"
                        + "操作符与之后相连的操作数类型不匹配");
            }

        }
        if (top > 0) {
            Token t = (Token) ts[top];
            u.operator = t.getExp();

            Object[] left = new Object[top];
            System.arraycopy(ts, 0, left, 0, top);

            Object[] right = new Object[length - top - 1];
            System.arraycopy(ts, top + 1, right, 0, length - top - 1);

            List ll = Arrays.asList(left);

            Unit lu = this.compile(ll, container);

            List rl = Arrays.asList(right);

            Unit ru = this.compile(rl, container);

            Operator op = (Operator) name2Operator
                    .get(t.getExp().toUpperCase());

            if (op.getSupportedInputTypes()[0].getClass().isAssignableFrom(
                    lu.returnedType.getClass())) {
                u.oprands.add(lu);
            } else {
                throw new TokenException("t.getExp().toUpperCase()"
                        + "操作符与之前相连的操作数类型不匹配");
            }

            if (op.getSupportedInputTypes()[1].getClass().isAssignableFrom(
                    ru.returnedType.getClass())) {
                u.oprands.add(ru);
            } else {
                throw new TokenException("t.getExp().toUpperCase()"
                        + "操作符与之后相连的操作数类型不匹配");
            }
            u.ref = op;
            u.returnedType = op.getReturnedType();
            u.type = Unit.OPERATION;
        }

        return u;
    }
拼装伪SQL
以递归的方式查询Unit，并根据相应的operator产生对应的SQL语句。