SQL解析

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前段时间主要研究了一下SQL语句的解析，主要的几个开源产品试用了一下。本文大概总结一下个人体会。

首先是ZQL，ZQL有个比较突出的优点是使用起来比较简单，基本上属于拿上手就可以用的。但支持的功能有限，selectItem可以是简单的表达式，但不支持查询作为一个selectItem，对于其他的子查询同样也不支持。

最终我选择使用了Jsqlparser，主要原因有两点：
1）功能强大，基本上能够覆盖所有的SQL语法（没有研究是不是包含了数据库特殊的关键字，如LIMIT ），包含UNION,GROUP BY,HAVING,ORDER BY,JOIN,SUB JOIN,SUB SELECT,FUNCTION等。支持SQL深层嵌套。
2）本身设计不错，使用起来感觉很灵活。Jsqlparser对于SQL的遍历采用了VISITOR模式可以很方便的遍历SQL语句。

下面主要介绍一下Jsqlparser在我的项目中的应用情况。

背景：通过SQL语句的解析，从而增强SQL语句增加特定的查询过滤条件（如：状态过滤、权限过滤等）


1）解析SQL
2）根据SQL中涉及的表增强SQL
3）重新生成ORACLE数据库的SQL

        CCJSqlParserManager parserManager = new CCJSqlParserManager();
        try {
            Select select = (Select) parserManager.parse(new StringReader(sql)); //解析SQL语句
            SelectBody body = select.getSelectBody(); 
            VisitContext vc = new VisitContext(filterContext, params);
            vc.setTableFilterFactory(tableFilterFactory);//表的字段过滤
            body.accept(new SelectVisitorImpl(vc)); //访问SQL并根据SQL中涉及的表来增强SQL
            ExpressionDeParser expressionDeParser = new ExpressionDeParser();
            StringBuffer stringBuffer = new StringBuffer();
            SelectDeParser deParser = new OracleSelectDeParser(expressionDeParser, stringBuffer); //针对ORACLE的SQL生成
            expressionDeParser.setSelectVisitor(deParser);
            expressionDeParser.setBuffer(stringBuffer);
            
            body.accept(deParser);
            return new FilterResult(deParser.getBuffer().toString(), vc.getResultSqlParams());
        } catch (JSQLParserException e) {
            throw new FilterException(e);
        }

接下去是各个VISITOR，用来访问解析后的SQL

public class SelectVisitorImpl extends AbstractVisitor implements SelectVisitor {

    public SelectVisitorImpl(VisitContext ctx) {
        super(ctx);
    }

    @SuppressWarnings("unchecked")
    public void visit(PlainSelect ps) {
        //SELECT ITEM访问
        List selectItems = ps.getSelectItems();
        for (SelectItem item : selectItems) {
            item.accept(new SelectItemVisitorImpl(this.getContext()));
        }

        //FROM访问
        FromItem from = ps.getFromItem();
        FromItemVisitorImpl fv = new FromItemVisitorImpl(context);
        from.accept(fv);

        //查询条件访问
        if (ps.getWhere() != null) {
            ps.getWhere().accept(new ExpressionVisitorImpl(this.getContext()));
        }

        //过滤增强的条件
        if (fv.getEnhancedCondition() != null) {
            if (ps.getWhere() != null) {
                Expression expr = new Parenthesis(ps.getWhere());
                AndExpression and = new AndExpression(fv.getEnhancedCondition(), expr);
                ps.setWhere(and);
            } else {
                ps.setWhere(fv.getEnhancedCondition());
            }
        }

        //JOIN表的访问
        List joins = ps.getJoins();
        if (CollectionUtil.isNotEmpty(joins)) {
            for (Join join : joins) {
                FromItemVisitorImpl tempfv = new FromItemVisitorImpl(context);
                join.getRightItem().accept(tempfv);
                if (join.getOnExpression() != null) {
                    join.getOnExpression().accept(new ExpressionVisitorImpl(this.getContext()));
                    if (tempfv.getEnhancedCondition() != null) {
                        Expression expr = new Parenthesis(join.getOnExpression());
                        AndExpression and = new AndExpression(tempfv.getEnhancedCondition(), expr);
                        join.setOnExpression(and);
                    }
                }
            }
        }

        //ORDER BY 访问
        List elements = ps.getOrderByElements();
        if (CollectionUtil.isNotEmpty(elements)) {
            for (OrderByElement e : elements) {
                e.getExpression().accept(new ExpressionVisitorImpl(this.getContext()));
            }
        }

        //GROUP BY的HAVING访问
        if (ps.getHaving() != null) {
            ps.getHaving().accept(new ExpressionVisitorImpl(this.getContext()));
        }
    }

    @SuppressWarnings("unchecked")
    public void visit(Union un) {
        List selects = un.getPlainSelects();
        for (PlainSelect select : selects) {
            select.accept(new SelectVisitorImpl(this.getContext()));
        }
        List elements = un.getOrderByElements();
        if (CollectionUtil.isNotEmpty(elements)) {
            for (OrderByElement e : elements) {
                e.getExpression().accept(new ExpressionVisitorImpl(this.getContext()));
            }
        }
    }

}

public class SelectItemVisitorImpl extends AbstractVisitor implements SelectItemVisitor {

    public SelectItemVisitorImpl(VisitContext ctx) {
        super(ctx);
    }

    public void visit(AllColumns ac) {
    }

    public void visit(AllTableColumns atc) {
    }

    public void visit(SelectExpressionItem sei) {
        sei.getExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

}

public class ItemsListVisitorImpl extends AbstractVisitor implements ItemsListVisitor {

    public ItemsListVisitorImpl(VisitContext ctx) {
        super(ctx);
    }

    public void visit(SubSelect ss) {
        ss.getSelectBody().accept(new SelectVisitorImpl(context));
    }

    @SuppressWarnings("unchecked")
    public void visit(ExpressionList el) {
        List list = el.getExpressions();
        if (CollectionUtil.isNotEmpty(list)) {
            for (Expression expr : list) {
                expr.accept(new ExpressionVisitorImpl(context));
            }
        }
    }

}

如果FROM的内容是table的话，则根据table的增强配置对SQL增强

public class FromItemVisitorImpl extends AbstractVisitor implements FromItemVisitor {
    private String varPattern = "@\\{\\s*?(\\w+)\\s*?\\}";
    private Expression enhancedCondition;

    public FromItemVisitorImpl(VisitContext ctx) {
        super(ctx);
    }

    public void visit(Table table) {
        Set filters = context.getTableFilterFactory().getTableFilter(table.getName());
        if (filters == null) {
            filters = Collections.emptySet();
        }
        for (FieldFilter ff : filters) {
            Column c = new Column(new Table(null, table.getAlias()), ff.getFieldName());
            JdbcParameter param = new JdbcParameter();
            Object fieldValue = getRawValue(ff.getFieldValue(), this.context.getFilterContext());
            Expression[] exps;
            if ("between".equalsIgnoreCase(ff.getOperator()) || "not between".equalsIgnoreCase(ff.getOperator())) {
                Object[] objs = (Object[]) fieldValue;
                this.getContext().getResultSqlParams().add(objs[0]);
                this.getContext().getResultSqlParams().add(objs[1]);
                exps = new Expression[] { c, param, param };
            } else if ("is null".equalsIgnoreCase(ff.getOperator()) || "is not null".equalsIgnoreCase(ff.getOperator())) {
                exps = new Expression[] { c };
            } else {
                this.getContext().getResultSqlParams().add(fieldValue);
                exps = new Expression[] { c, param };
            }
            Expression operator = this.getOperator(ff.getOperator(), exps);
            if (this.enhancedCondition != null) {
                enhancedCondition = new AndExpression(enhancedCondition, operator);
            } else {
                enhancedCondition = operator;
            }
        }
    }

    public void visit(SubSelect ss) {
        ss.getSelectBody().accept(new SelectVisitorImpl(this.getContext()));
    }

    public void visit(SubJoin sj) {
        Join join = sj.getJoin();
        join.getRightItem().accept(new FromItemVisitorImpl(this.getContext()));
        join.getOnExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    private Expression getOperator(String op, Expression[] exp) {
        if ("=".equals(op)) {
            EqualsTo eq = new EqualsTo();
            eq.setLeftExpression(exp[0]);
            eq.setRightExpression(exp[1]);
            return eq;
        } else if (">".equals(op)) {
            GreaterThan gt = new GreaterThan();
            gt.setLeftExpression(exp[0]);
            gt.setRightExpression(exp[1]);
            return gt;
        } else if (">=".equals(op)) {
            GreaterThanEquals geq = new GreaterThanEquals();
            geq.setLeftExpression(exp[0]);
            geq.setRightExpression(exp[1]);
            return geq;
        } else if ("<".equals(op)) {
            MinorThan mt = new MinorThan();
            mt.setLeftExpression(exp[0]);
            mt.setRightExpression(exp[1]);
            return mt;
        } else if ("<=".equals(op)) {
            MinorThanEquals leq = new MinorThanEquals();
            leq.setLeftExpression(exp[0]);
            leq.setRightExpression(exp[1]);
            return leq;
        } else if ("<>".equals(op)) {
            NotEqualsTo neq = new NotEqualsTo();
            neq.setLeftExpression(exp[0]);
            neq.setRightExpression(exp[1]);
            return neq;
        } else if ("is null".equalsIgnoreCase(op)) {
            IsNullExpression isNull = new IsNullExpression();
            isNull.setNot(false);
            isNull.setLeftExpression(exp[0]);
            return isNull;
        } else if ("is not null".equalsIgnoreCase(op)) {
            IsNullExpression isNull = new IsNullExpression();
            isNull.setNot(true);
            isNull.setLeftExpression(exp[0]);
            return isNull;
        } else if ("like".equalsIgnoreCase(op)) {
            LikeExpression like = new LikeExpression();
            like.setNot(false);
            like.setLeftExpression(exp[0]);
            like.setRightExpression(exp[1]);
            return like;
        } else if ("not like".equalsIgnoreCase(op)) {
            LikeExpression nlike = new LikeExpression();
            nlike.setNot(true);
            nlike.setLeftExpression(exp[0]);
            nlike.setRightExpression(exp[1]);
            return nlike;
        } else if ("between".equalsIgnoreCase(op)) {
            Between bt = new Between();
            bt.setNot(false);
            bt.setLeftExpression(exp[0]);
            bt.setBetweenExpressionStart(exp[1]);
            bt.setBetweenExpressionEnd(exp[2]);
            return bt;
        } else if ("not between".equalsIgnoreCase(op)) {
            Between bt = new Between();
            bt.setNot(true);
            bt.setLeftExpression(exp[0]);
            bt.setBetweenExpressionStart(exp[1]);
            bt.setBetweenExpressionEnd(exp[2]);
            return bt;
        }
        throw new FilterException("Unknown operator:" + op);
    }

    protected Object getRawValue(Object value, Map context) {
        if (context == null) {
            return value;
        }
        if (value instanceof String) {
            String v = (String) value;
            Pattern pattern = Pattern.compile(varPattern);
            Matcher matcher = pattern.matcher(v);
            if (matcher.find()) {
                return context.get(matcher.group(1));
            }
        }
        return value;
    }

    public Expression getEnhancedCondition() {
        return enhancedCondition;
    }

}

1）对JDBC parameter做了处理，如果参数为NULL则自动忽略该parameter，忽略后需要处理and or between 等情况
   如：where name=? and age=? ，假如name对应的参数为null，则条件改为where 1=1 and age=?，如果是or的话则改为 where 1=0 or age=?

public class ExpressionVisitorImpl extends AbstractVisitor implements ExpressionVisitor {

    public ExpressionVisitorImpl(VisitContext ctx) {
        super(ctx);
    }

    public void visit(NullValue nv) {
    }

    public void visit(Function f) {
    }

    public void visit(InverseExpression ie) {
    }

    public void visit(JdbcParameter jp) {
        this.getContext().getResultSqlParams().add(context.removeFirstParam());
    }

    public void visit(DoubleValue dv) {
    }

    public void visit(LongValue lv) {
    }

    public void visit(DateValue dv) {
    }

    public void visit(TimeValue tv) {
    }

    public void visit(TimestampValue tv) {
    }

    public void visit(Parenthesis parenthesis) {
        ExpressionVisitorImpl ev = new ExpressionVisitorImpl(context);
        parenthesis.getExpression().accept(ev);
        if (ev.isNotValid()) {
            parenthesis.setExpression(this.createTrueEquals());
        }
    }

    public void visit(StringValue s) {
    }

    public void visit(Addition a) {
    }

    public void visit(Division d) {
    }

    public void visit(Multiplication m) {
    }

    public void visit(Subtraction s) {
    }

    public void visit(AndExpression and) {
        ExpressionVisitorImpl left = new ExpressionVisitorImpl(this.getContext());
        and.getLeftExpression().accept(left);
        if (left.isNotValid()) {
            and.setLeftExpression(this.createTrueEquals());
        }
        ExpressionVisitorImpl right = new ExpressionVisitorImpl(this.getContext());
        and.getRightExpression().accept(right);
        if (right.isNotValid()) {
            and.setRightExpression(this.createTrueEquals());
        }
    }

    public void visit(OrExpression or) {
        ExpressionVisitorImpl left = new ExpressionVisitorImpl(this.getContext());
        or.getLeftExpression().accept(left);
        if (left.isNotValid()) {
            or.setLeftExpression(this.createFalseEquals());
        }
        ExpressionVisitorImpl right = new ExpressionVisitorImpl(this.getContext());
        or.getRightExpression().accept(right);
        if (right.isNotValid()) {
            or.setRightExpression(this.createFalseEquals());
        }
    }

    public void visit(Between btw) {
        Expression start = btw.getBetweenExpressionStart();
        Expression end = btw.getBetweenExpressionEnd();
        if (start instanceof JdbcParameter && end instanceof JdbcParameter) {
            Object o1 = this.context.getFirstParam();
            Object o2 = this.context.getParam(1);
            if (o1 == null || o2 == null) {
                this.context.removeFirstParam();
                this.context.removeFirstParam();
                this.setValid(false);
                return;
            }
        } else if (start instanceof JdbcParameter || end instanceof JdbcParameter) {
            Object o1 = this.context.getFirstParam();
            if (o1 == null) {
                this.context.removeFirstParam();
                this.setValid(false);
                return;
            }
        }
        btw.getLeftExpression().accept(new ExpressionVisitorImpl(context));
        btw.getBetweenExpressionStart().accept(new ExpressionVisitorImpl(context));
        btw.getBetweenExpressionEnd().accept(new ExpressionVisitorImpl(context));
    }

    public void visit(EqualsTo eq) {
        if (eq.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
                return;
            }
        }
        eq.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        eq.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(GreaterThan gt) {
        if (gt.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
            }
        }
        gt.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        gt.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(GreaterThanEquals gte) {
        if (gte.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
            }
        }
        gte.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        gte.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(InExpression in) {
        ItemsList list = in.getItemsList();
        list.accept(new ItemsListVisitorImpl(context));
    }

    public void visit(IsNullExpression ine) {
    }

    public void visit(LikeExpression le) {
        if (le.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
            }
        }
        le.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        le.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(MinorThan mt) {
        if (mt.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
            }
        }
        mt.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        mt.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(MinorThanEquals mte) {
        if (mte.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
            }
        }
        mte.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        mte.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(NotEqualsTo neq) {
        if (neq.getRightExpression() instanceof JdbcParameter) {
            Object o = this.context.getFirstParam();
            if (o == null) {
                this.setValid(false);
                this.getContext().removeFirstParam();
                return;
            }
        }
        neq.getLeftExpression().accept(new ExpressionVisitorImpl(this.getContext()));
        neq.getRightExpression().accept(new ExpressionVisitorImpl(this.getContext()));
    }

    public void visit(Column c) {
    }

    public void visit(SubSelect ss) {
        ss.getSelectBody().accept(new SelectVisitorImpl(context));
    }

    public void visit(CaseExpression ce) {
    }

    public void visit(WhenClause wc) {
    }

    public void visit(ExistsExpression ee) {
    }

    public void visit(AllComparisonExpression ace) {
    }

    public void visit(AnyComparisonExpression ace) {
    }

    public void visit(Concat c) {
    }

    public void visit(Matches m) {
    }

    public void visit(BitwiseAnd ba) {
    }

    public void visit(BitwiseOr bo) {
    }

    public void visit(BitwiseXor bx) {
    }

    private EqualsTo createTrueEquals() {
        EqualsTo eq = new EqualsTo();
        eq.setLeftExpression(new LongValue("1"));
        eq.setRightExpression(new LongValue("1"));
        return eq;
    }

    private EqualsTo createFalseEquals() {
        EqualsTo eq = new EqualsTo();
        eq.setLeftExpression(new LongValue("1"));
        eq.setRightExpression(new LongValue("0"));
        return eq;
    }

}

增强后SQL语句的重新生成，根据ORACLE的语法重写了几个生成的方法

public class OracleSelectDeParser extends SelectDeParser {

    public OracleSelectDeParser(ExpressionDeParser expressionDeParser, StringBuffer sb) {
        super(expressionDeParser, sb);
    }

    /**
     * 重写父类方法，去掉父类方法中table前的as
     */
    public void visit(Table tableName) {
        buffer.append(tableName.getWholeTableName());
        String alias = tableName.getAlias();
        if (alias != null && StringUtil.isNotEmpty(alias)) {
            buffer.append(" ");
            buffer.append(alias);
        }
    }

    /**
     * 重写父类方法，在JOIN之前增加空格
     */
    @SuppressWarnings("unchecked")
    public void deparseJoin(Join join) {
        if (join.isSimple()) {
            buffer.append(", ");
        } else {
            buffer.append(" ");
            if (join.isRight()) {
                buffer.append("RIGHT ");
            } else if (join.isNatural()) {
                buffer.append("NATURAL ");
            } else if (join.isFull()) {
                buffer.append("FULL ");
            } else if (join.isLeft()) {
                buffer.append("LEFT ");
            }
            if (join.isOuter()) {
                buffer.append("OUTER ");
            } else if (join.isInner()) {
                buffer.append("INNER ");
            }
            buffer.append("JOIN ");
        }

        FromItem fromItem = join.getRightItem();
        fromItem.accept(this);
        if (join.getOnExpression() != null) {
            buffer.append(" ON ");
            join.getOnExpression().accept(expressionVisitor);
        }
        if (join.getUsingColumns() != null) {
            buffer.append(" USING ( ");
            for (Iterator iterator = join.getUsingColumns().iterator(); iterator.hasNext();) {
                Column column = iterator.next();
                buffer.append(column.getWholeColumnName());
                if (iterator.hasNext()) {
                    buffer.append(" ,");
                }
            }
            buffer.append(")");
        }
    }

}