How to create factory element locator contained from multiple joined locators in Java Selenium

Question

For example, the page has a container field with a locator id = "test1" and another field with a locator id = "field1"

The joined locator should search in the locator id = "test1" for the locator id = "field1": locator1.findElement().findElement((By) locator2)

How to create an element locator contained from multiple merged locators in Java Selenium

In the code, it is indicated as mergeLocator, but I do not know how to do this.

ElementLocator mergeLocator = locator1 + locator2;

My code:

import lombok.SneakyThrows;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.pagefactory.DefaultFieldDecorator;
import org.openqa.selenium.support.pagefactory.ElementLocator;
import org.openqa.selenium.support.pagefactory.ElementLocatorFactory;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;

public class ElementsDecorator extends DefaultFieldDecorator {
    private WebDriver driver;

    public ElementsDecorator(ElementLocatorFactory factory, WebDriver driver) {
        super(factory);
        this.driver = driver;
    }

    @SneakyThrows
    @Override
    public Object decorate(ClassLoader loader, Field field) {
        ElementLocator locator1 = factory.createLocator(field);
        ElementLocator locator2 = factory.createLocator(field.getDeclaringClass().getDeclaredField("container"));
        ElementLocator mergeLocator = locator1 + locator2;
        return createElement(loader, mergeLocator, field.getType());
    }
    
    protected <T> T createElement(ClassLoader loader, ElementLocator locator, Class<?> tClass) {
        WebElement proxy = proxyForLocator(loader, locator);
        try {
            return (T) tClass.getConstructor(WebElement.class, WebDriver.class).newInstance(proxy, driver);
        } catch (NoSuchMethodException | SecurityException | IllegalAccessException | InstantiationException |
                 InvocationTargetException e) {
            throw new AssertionError("WebElement can't be represented as " + tClass);
        }
    }
}