techupskills: create functional documentation explaining the various public APIs in #file:EmployeeController.java 

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# Functional Documentation for `EmployeeController`

The `EmployeeController` class provides RESTful APIs to interact with the Employee Directory. It allows users to retrieve employee details based on various search criteria such as employee ID, age, city, or a combination of age and city. Below is the detailed documentation for each API endpoint:

---

## 1. **Get All Employees**

### Endpoint
```
GET /employees/all
```

### Description
Fetches a list of all employees in the directory.

### Response
- **200 OK**: Returns a list of all employees.
- **500 Internal Server Error**: Returns an error message if an exception occurs.

---

## 2. **Search Employee by Employee ID**

### Endpoint
```
GET /employees/{employeeId}
```

### Description
Fetches the details of a specific employee based on their unique employee ID.

### Parameters
- **Path Variable**: `employeeId` (Integer) - The ID of the employee to be retrieved.

### Response
- **200 OK**: Returns the employee details.
- **500 Internal Server Error**: Returns an error message if an exception occurs.

---

## 3. **Filter Employees by Age**

### Endpoint
```
GET /employees/greaterThanAge/{age}
```

### Description
Fetches a list of employees whose age is greater than the specified value.

### Parameters
- **Path Variable**: `age` (Integer) - The age threshold for filtering employees.

### Response
- **200 OK**: Returns a list of employees matching the criteria.
- **500 Internal Server Error**: Returns an error message if an exception occurs.

---

## 4. **Filter Employees by City**

### Endpoint
```
GET /employees/fromCity/{cityName}
```

### Description
Fetches a list of employees who are from the specified city.

### Parameters
- **Path Variable**: `cityName` (String) - The name of the city to filter employees by.

### Response
- **200 OK**: Returns a list of employees matching the criteria.
- **500 Internal Server Error**: Returns an error message if an exception occurs.

---

## 5. **Filter Employees by Age and City**

### Endpoint
```
GET /employees/filterByAgeAndCity
```

### Description
Fetches a list of employees who are from a specified city and whose age is greater than the specified value.

### Parameters
- **Header**: `schoolId` (String) - The school ID for authentication or tracking purposes.
- **Query Parameter**: `age` (Integer) - The age threshold for filtering employees.
- **Query Parameter**: `cityName` (String) - The name of the city to filter employees by.

### Response
- **200 OK**: Returns a list of employees matching the criteria.
- **500 Internal Server Error**: Returns an error message if an exception occurs.

---

## Notes
- All endpoints produce responses in `application/json` format.
- Proper logging is implemented for debugging and error tracking.
- Swagger annotations (`@Api`, `@ApiOperation`, `@ApiParam`, `@ApiImplicitParam`) are used to document the APIs for integration with Swagger UI.
