We would continue from Part 21. You will learn how to update a record and delete a record. You will also learn about CascadeTypes and FetchTypes in Hibernate. So let’s get stated!<\/p>\n
<\/p>\n
Part 21 – Updating Location Details<\/strong><\/p>\n To update Location details, follows the steps below:<\/p>\n Step 1:<\/strong> Open the LocationController file<\/p>\n Step 2:<\/strong> Copy and paste the code below<\/p>\n <\/p>\n <\/p>\n Step 3:<\/strong> Open the LocationService and paste the code below:<\/p>\n <\/p>\n <\/p>\n Step 4:<\/strong> Launch the application. Use Advanced REST Client to attempt to update a location. Set the method this time to PUT<\/p>\n <\/p>\n Part 22 – Updating User Details<\/strong><\/p>\n To update Location details, follows the steps below:<\/p>\n Step 1:<\/strong> Open the UserController file<\/p>\n Step 2:<\/strong> Copy and paste the code below<\/p>\n <\/p>\n <\/p>\n Step 3:<\/strong> Open the UserService and paste the code below:<\/p>\n <\/p>\n <\/p>\n Step 4:<\/strong> Relaunch and test<\/p>\n <\/p>\n Part 23 – Updating Post Details<\/strong><\/p>\n To update Location details, follows the steps below:<\/p>\n Step 1:<\/strong> Open the PostController file<\/p>\n Step 2:<\/strong> Copy and paste the code below<\/p>\n <\/p>\n <\/p>\n Step 3:<\/strong> Open the PostService and paste the code below:<\/p>\n <\/p>\n <\/p>\n Step 4:<\/strong> Relaunch and test<\/p>\n <\/p>\n Part 24: Deleting a Post<\/strong><\/p>\n Deleting a Post would be quite straightforward as the Post object does not have any child objects. So let’s get it done!<\/p>\n Step 1:<\/strong> Copy the code below and paste in the PostController<\/p>\n <\/p>\n Step 2:<\/strong> Copy the code below and paste into the PostService<\/p>\n <\/p>\n Step 3:<\/strong> Relaunch the application and test it using r the REST client. Either way, check that the post was deleted using H2 Console.<\/p>\n <\/p>\n Part 25: Deleting a User<\/strong><\/p>\n The question about deleting a User is this: If we delete a particular user, what will happen to all the posts belonging to this user? Well, before we answer this question, let’s try to delete a user using the method used in deleting post.<\/p>\n Step 1:<\/strong> Copy the code below and paste in the UserController<\/p>\n <\/p>\n Step 2:<\/strong> Copy the code below and paste into the UserService<\/p>\n <\/p>\n Step 3:<\/strong> Relaunch the application and test it using\u00a0 REST client. Try to delete user\/1. You will notice that the delete operation fails. You receive a message like:<\/p>\n <\/p>\n The reason for this error is that we try to delete a user who has posts.( an entity with child entities)<\/p>\n Let’s now solve this problem by talking about CascadeTypes<\/p>\n <\/p>\n Part 26: CascadeType in Hibernate<\/strong><\/p>\n The CascadeType answers the question of what will happen when you delete an object has children reference objects. Now a number of things could happen<\/p>\n Let’s not go to far! We’ll only use the second one: CascadeType.ALL<\/p>\n To solve the problem simply take the step below:<\/p>\n Step 1:<\/strong> Open the User model<\/p>\n Step 2:<\/strong> Add cascade = CascadeType.ALL\u00a0 to the @OneToMany annotation. It would be as shown below:<\/p>\n@PutMapping<\/span>(<\/span>\"\/location\/{id}\/update\"<\/span>)<\/span>\npublic<\/span> void<\/span> UpdateLocation<\/span>(<\/span>@RequestBody<\/span> Location location)<\/span> {<\/span>\n\tlocationService.<\/span>UpdateLocation<\/span>(<\/span>location);<\/span>\n}<\/span>\n<\/pre>\npublic<\/span> void<\/span> UpdateLocation<\/span>(<\/span>Location location)<\/span> {<\/span>\n\tlocationRepository.<\/span>save<\/span>(<\/span>location);<\/span>\n}<\/span>\n<\/pre>\n@PutMapping<\/span>(<\/span>\"\/user\/{id}\/update\"<\/span>)<\/span>\npublic<\/span> void<\/span> UpdateUsern<\/span>(<\/span>@RequestBody<\/span> User user )<\/span> {<\/span>\n\tuserService.<\/span>UpdateUser<\/span>(user<\/span>);<\/span>\n}<\/span>\n<\/pre>\npublic<\/span> void<\/span> UpdateUser<\/span>(User user<\/span>)<\/span> {<\/span>\n\tuserRepository.<\/span>save<\/span>(<\/span>user);<\/span>\n}<\/span><\/pre>\n@PutMapping<\/span>(<\/span>\"\/post\/{id}\/update\"<\/span>)<\/span>\npublic<\/span> void<\/span> UpdatePost<\/span>(<\/span>@RequestBody<\/span> Post post)<\/span> {<\/span>\n\tpostService.<\/span>UpdatePost<\/span>(<\/span>post);<\/span>\n}<\/span>\n<\/pre>\npublic<\/span> void<\/span> UpdatePost<\/span>(<\/span>Post post)<\/span> {<\/span>\n\tpostRepository.<\/span>save<\/span>(<\/span>post);<\/span>\n}<\/span><\/pre>\n@DeleteMapping<\/span>(<\/span>\"\/post\/{id}\/delete\"<\/span>)<\/span>\npublic<\/span> void<\/span> DeletePost<\/span>(<\/span>@PathVariable<\/span> Integer id)<\/span> {<\/span>\n postService.<\/span>DeletePost<\/span>(<\/span>id);<\/span>\n}<\/span>\n<\/pre>\npublic<\/span> void<\/span> DeletePost<\/span>(<\/span>Integer id)<\/span> {<\/span>\n postRepository.<\/span>deleteById<\/span>(<\/span>id);<\/span>\n}<\/span>\n<\/pre>\n@DeleteMapping<\/span>(<\/span>\"\/user\/{id}\/delete\"<\/span>)<\/span>\npublic<\/span> void<\/span> DeleteUser<\/span>(<\/span>@PathVariable<\/span> Integer id)<\/span> {<\/span>\n userService.<\/span>DeleteUser<\/span>(<\/span>id);<\/span>\n}<\/span>\n<\/pre>\npublic<\/span> void<\/span> DeleteUser<\/span>(<\/span>Integer id)<\/span> {<\/span>\n userRepository.<\/span>deleteById<\/span>(<\/span>id);<\/span>\n}<\/span>\n<\/pre>\n{\n\"timestamp\"<\/span>: \"2019-09-02T22:23:30.879+0000\"<\/span>,\n\"status\"<\/span>: 500<\/span>,\n\"error\"<\/span>: \"Internal Server Error\"<\/span>,\n\"message\"<\/span>: \"could not execute statement; SQL [n\/a]; constraint [\"<\/span>FK<\/span>2<\/span>SF<\/span>14<\/span>YOUCWQSO<\/span>9<\/span>PDCH<\/span>0<\/span>UIWPEM<\/span>: PUBLIC.POST<\/span> FOREIGN<\/span> KEY(USERID)<\/span> REFERENCES<\/span> PUBLIC.USER(ID)<\/span> (<\/span>1<\/span>)<\/span>\"; SQL statement: delete from user where id=? [23503-199]]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement\"<\/span>,\n\"path\"<\/span>: \"\/user\/1\/delete\"<\/span>\n}\n<\/pre>\n\n