init

src/main/kotlin/shared/exceptions/ChangeUsernameException.kt

@@ -0,0 +1,4 @@
+package shared.exceptions
+
+class ChangeUsernameException(msg: String) : RuntimeException(msg) {
+}

src/main/kotlin/shared/exceptions/NotFoundException.kt

@@ -0,0 +1,4 @@
+package shared.exceptions
+
+class NotFoundException(msg: String) : RuntimeException(msg) {
+}

src/main/kotlin/shared/validation/AbstractValidationHandler.kt

@@ -0,0 +1,15 @@
+package shared.validation
+
+abstract class AbstractValidationHandler<T> : ValidationHandler<T> {
+    private lateinit var nextHandler: ValidationHandler<T>
+
+    override fun setNext(handler: ValidationHandler<T>) {
+        nextHandler = handler
+    }
+
+    protected fun next(context: T) {
+        if (::nextHandler.isInitialized) {
+            nextHandler.validate(context)
+        }
+    }
+}

src/main/kotlin/shared/validation/ValidationChain.kt

@@ -0,0 +1,22 @@
+package shared.validation
+
+class ValidationChain<T> {
+    private var firstHandler: ValidationHandler<T>? = null
+    private var lastHandler: ValidationHandler<T>? = null
+
+    fun add(handler: ValidationHandler<T>): ValidationChain<T> {
+        if (firstHandler == null) {
+            firstHandler = handler
+            lastHandler = handler
+        } else {
+            lastHandler?.setNext(handler)
+            lastHandler = handler
+        }
+        return this
+    }
+
+    fun validate(context: T) {
+        firstHandler?.validate(context)
+            ?: throw IllegalStateException("验证链未初始化")
+    }
+}

src/main/kotlin/shared/validation/ValidationHandler.kt

@@ -0,0 +1,6 @@
+package shared.validation
+
+interface ValidationHandler<T> {
+    fun validate(context: T)
+    fun setNext(handler: ValidationHandler<T>)
+}