jeecgboot/JeecgBoot · warning · RuntimeException

不支持的运算符: {op}

Error message

不支持的运算符: {op}

What it means

Inside the 'calculate' tool of the MCP demo, the operator switch accepts only '+', '-', '*', '/'. Any other operator string throws a RuntimeException that becomes a tool-call error returned to the MCP client. Note '/' with b==0 yields NaN rather than erroring.

Source

Thrown at jeecg-boot/jeecg-boot-module/jeecg-module-demo/src/main/java/org/jeecg/modules/demo/mcp/McpDemoController.java:289

                if (name == null || name.isEmpty()) {
                    name = "World";
                }
                yield "你好, " + name + "! 欢迎使用 JeecgBoot MCP 服务!";
            }
            case "get_time" -> {
                yield "当前时间: " + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
            }
            case "calculate" -> {
                double a = arguments.getDoubleValue("a");
                double b = arguments.getDoubleValue("b");
                String op = arguments.getString("operator");
                if (op == null) op = "+";
                double res = switch (op) {
                    case "+" -> a + b;
                    case "-" -> a - b;
                    case "*" -> a * b;
                    case "/" -> b != 0 ? a / b : Double.NaN;
                    default -> throw new RuntimeException("不支持的运算符: " + op);
                };
                yield String.format("%.2f %s %.2f = %.2f", a, op, b, res);
            }
            default -> throw new RuntimeException("未知工具: " + toolName);
        };
        
        return Map.of(
                "content", List.of(Map.of(
                        "type", "text",
                        "text", result
                ))
        );
    }

    /**
     * 使用说明页面
     */
    @IgnoreAuth

View on GitHub (pinned to 96fb33f5ec)

Solutions

1. Use one of +, -, *, /.
2. If more operators are needed, extend the switch and document them in the tool schema.

Example fix

// before
default -> throw new RuntimeException("不支持的运算符: " + op);
// after - accept extra operators
case "%", "mod" -> b != 0 ? a % b : Double.NaN;
case "^", "**" -> Math.pow(a, b);

private static final Set<String> ALLOWED_OPS = Set.of("+","-","*","/","%","^");
String op = arguments.getString("operator");
if (op != null && !ALLOWED_OPS.contains(op)) {
    // return a tool error: unsupported operator
}

// tool-call errors are returned to the client as a content result; ensure the message
// lists the allowed operators so the caller can self-correct.

When it happens

Trigger: Client passes an operator like 'mod', '^', 'div', '**', or a localized symbol not in the switch.

Common situations: Client expects extended math; user-typed operator; locale-specific symbols.

Related errors

• 未知方法: {method}
• 未知工具: {toolName}
• 模板缺少参数：${item}
• The file name can not null
• 非法存储路径，路径包含遍历字符: {storePath}

AI-assisted analysis of jeecgboot/JeecgBoot@96fb33f5ec (2026-08-14). Data as JSON: /api/errors/193ea18d99230628. Report an issue: GitHub.