字符匹配之模仿mybatis词解析器

╰+攻爆jí腚メ 2022-09-02 14:49 138阅读 0赞

public static void main(String[] args) {
            String text="select * from usr where id=#{id} and name=#{id}";
            HashMap<String, Object> map = new HashMap<>();
            map.put("id","alex");
            System.out.printf(parseSeql(text,map));
        }
        public static String parseSeql(String sql, Map<String,Object> nameArgMap){
            StringBuilder sb = new StringBuilder();
            int len=sql.length();
    //        char[] arr=sql.toCharArray();
            for (int i = 0; i < len; i++) {
                if(sql.charAt(i) =='#'){
                    int nextIndex=i+1;
                    if (sql.charAt(nextIndex)!='{'){
                            throw new RuntimeException(String.format("此处应该为#{\nsql:%s\n index:%d:",sb.toString(),nextIndex));
                    }
                    StringBuilder argSB = new StringBuilder();
                    i=parseSeqlArgs(argSB,sql,nextIndex);
                    String argName=argSB.toString();
                    Object ageValue=nameArgMap.get(argName);
                    if (ageValue == null) {
                        throw new RuntimeException(String.format("找不到参数#{\nsql:%s\n index:%d:",sb.toString(),nextIndex));
                    }
                    sb.append(ageValue.toString());
                    continue;
    
                }
                sb.append(sql.charAt(i));
            }
    
            return sb.toString();
        }
    
        private static int parseSeqlArgs(StringBuilder argSB, String sql, int nextIndex) {
            nextIndex++;
            for (;nextIndex<sql.length();nextIndex++){
                char c=sql.charAt(nextIndex);
                if (c !='}') {
                    argSB.append(c);
                    continue;
                }
                if(c=='}'){
                    return nextIndex;
                }
            }
            throw new RuntimeException(String.format("缺少右括号#{\nsql:%s\n index:%d:",argSB.toString(),nextIndex));
        }
    }