Fixed OneToOne and OneToMany, so that the mapped entities are not deleted, Used @CreationTimestamp and @UpdateTimestamp to update the creation and update times automatically. Return Kotlin Triple in BookService.kt to return a Triple <>

Author: ajaycode

JPATableJoins/build.gradle.kts

@@ -8,7 +8,7 @@ plugins {
 	kotlin("plugin.jpa") version "1.4.30"
 }
 
-group = "com.oreilly"
+group = "com.hello"
 version = "0.0.1-SNAPSHOT"
 java.sourceCompatibility = JavaVersion.VERSION_11
 

JPATableJoins/src/main/kotlin/com/hello/bookinventory/controller/BookController.kt

@@ -7,6 +7,7 @@ import org.apache.logging.log4j.LogManager
 import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.web.bind.annotation.RequestMapping
 import org.springframework.web.bind.annotation.RestController
+import kotlin.Triple as KotlinTriple
 
 @RestController
 class BookController {
@@ -43,14 +44,24 @@ class BookController {
         return outputString
     }
 
+    //curl http://localhost:8080/deleteBook
+    // Deletes a random book from the book table
     @RequestMapping ("/deleteBook")
     fun deleteBook () : String {
-        if (bookService.deleteBook ())
+        val returnTriple  =  bookService.deleteBook ()
+        if (returnTriple.first == true)
         {
-            return "Book Deleted"
+            return "Book ${returnTriple.second} with title ${returnTriple.third} Deleted"
         }
         else {
             return "Book could not be deleted"
         }
     }
+
+    //curl http://localhost:8080/updateBook
+    // Updates the title of the book from X to X[Updated].  The timestamp should also be updated.
+    @RequestMapping("/updateBook")
+    fun updateBook (): String {
+        return bookService.updateBook()
+    }
 }

JPATableJoins/src/main/kotlin/com/hello/bookinventory/dao/BookRepository.kt

@@ -6,4 +6,5 @@ import org.springframework.stereotype.Repository
 
 @Repository
 interface BookRepository : JpaRepository <Book, Long> {
+
 }

JPATableJoins/src/main/kotlin/com/hello/bookinventory/model/Author.kt

@@ -10,7 +10,7 @@ data class Author (
 
     var name : String = "",
 
-    @OneToMany(cascade = arrayOf(CascadeType.ALL), mappedBy = "author", orphanRemoval = true)
+    @OneToMany(cascade = arrayOf(CascadeType.ALL), mappedBy = "author", orphanRemoval = false)
     var bookList : List<Book> = mutableListOf()
 ){
     override fun toString(): String {

JPATableJoins/src/main/kotlin/com/hello/bookinventory/model/Book.kt

@@ -1,20 +1,33 @@
 package com.hello.bookinventory.model
 
+import org.hibernate.annotations.CreationTimestamp
+import org.hibernate.annotations.UpdateTimestamp
+import java.util.*
 import javax.persistence.*
 
 @Entity
 data class Book(
     @Id
-    @GeneratedValue(strategy=GenerationType.IDENTITY)
-    var id : Long = 0,
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    var id: Long = 0,
 
     var title: String = "",
 
-    @OneToOne(cascade = arrayOf(CascadeType.ALL))
+    @OneToOne(orphanRemoval = false)
     @JoinColumn(name = "aid")
-    var author : Author? = null
+    val author: Author? = null,
+
+    @CreationTimestamp
+    @Temporal(TemporalType.TIMESTAMP)
+    var createdDate: Date? = null,
+
+    @UpdateTimestamp
+    @Temporal(TemporalType.TIMESTAMP)
+    var modifiedDate: Date? = null
 ) {
     override fun toString(): String {
         return title
     }
+
+
 }

JPATableJoins/src/main/kotlin/com/hello/bookinventory/service/BookService.kt

@@ -7,7 +7,9 @@ import com.hello.bookinventory.model.Book
 import org.apache.logging.log4j.LogManager
 import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.stereotype.Service
+import java.util.*
 import kotlin.random.Random
+import kotlin.Triple as KotlinTriple
 
 @Service
 class BookService {
@@ -43,15 +45,55 @@ class BookService {
 
     }
 
-    fun deleteBook () : Boolean {
+    fun deleteBook () : KotlinTriple<Boolean, Long, String> {
         val bookCount = bookRepository.count()
-        val bookToDelete : Long = Random.nextLong(0, bookCount -1)
+        val bookToDelete : Long = Random.nextLong(1, bookCount)
         logger.info ("Will attempt to delete book # $bookToDelete")
         if (bookRepository.existsById(bookToDelete))
         {
-            bookRepository.deleteById(bookToDelete)
+            val book  = bookRepository.findById(bookToDelete)
+            var title : String = ""
+            if (book.isPresent())
+               title = book.get().title
+            logger.info ("Title of book to be deleted : ${title}")
+            var status : Boolean = true
+            try {
+                bookRepository.deleteById(bookToDelete)
+            }
+            catch (e: Exception)
+            {
+                logger.error("Unable to delete book # $bookToDelete, with title ${title} .")
+                logger.error ("Exception thrown. ${e.message}")
+                status = false
+            }
+            if (status == true)
+                return KotlinTriple(true, second = bookToDelete, third = title)
         }
-        return  !(bookRepository.existsById(bookToDelete))
+        return KotlinTriple(false, second = 0L, third = "null")
+    }
+
+
+    fun updateBook () : String {
+        val bookCount = bookRepository.count()
+        // var bookExists : Boolean = true
+        var i : Long = 1
+        while (!bookRepository.existsById(i) && i <= bookCount ){
+            i++
+            logger.info ("No book found with id # $i .")
+
+        }
+        if (i <= bookCount && bookRepository.existsById(i)){
+            var book : Book = bookRepository.getOne(i)
+            book.title = book.title + "[Updated]"
+            var savedBook : Book = bookRepository.save(book)
+            return ("Title was updated to ${savedBook.title}")
+        }
+        else {
+            return ("Title was not updated")
+        }
+
+
+
     }
 
     fun findAllAuthors () : List <Author> {