gsonpath.util.FieldGetterFinder.kt Maven / Gradle / Ivy

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An annotation processor which generates Type Adapters for the Google Gson library

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package gsonpath.util

import java.util.*
import javax.lang.model.element.Element
import javax.lang.model.element.ElementKind
import javax.lang.model.element.TypeElement
import javax.lang.model.type.ExecutableType

class FieldGetterFinder(private val typeHandler: TypeHandler) {
    /**
     * Attempts to find a logical getter method for a variable.
     *
     * For example, the following getter method names are valid for a variable named 'foo':
     * 'foo()', 'isFoo()', 'hasFoo()', 'getFoo()'
     *
     * If no getter method is found, an exception will be fired.
     *
     * @param parentElement the parent element of the field.
     * @param variableElement the field element we want to find the getter method for.
     */
    fun findGetter(parentElement: TypeElement, variableElement: Element): Element? {
        return typeHandler.getAllMembers(parentElement)
                .asSequence()
                .filter { it.kind == ElementKind.METHOD }
                .filter { isMethodNameGetter(it, variableElement) }
                .find { (it.asType() as ExecutableType).parameterTypes.size == 0 }
    }

    /**
     * Determines if the method name either matches the variable name, or starts with a standard getter prefix.
     */
    private fun isMethodNameGetter(methodElement: Element, variableElement: Element): Boolean {
        val remainder = methodElement.simpleName.toString()
                .toLowerCase(Locale.ENGLISH)
                .replace(variableElement.simpleName.toString().toLowerCase(Locale.ENGLISH), "")
        return arrayOf("", "is", "has", "get").contains(remainder)
    }
}