Bạn có thể thêm bản đồ của riêng bạn cho mã phản hồi cụ thể. Ví dụ, nếu bạn muốn bản đồ tất cả các yêu cầu cho một cái gì đó mà không thể được tìm thấy để hành động mặc định trong StoreController, bạn có thể làm như vậy với các bản đồ thể hiện trong bảng liệt kê 6-20. Ví dụ 6-20 | 154 CHAPTER 6 MAPPING URLS You can add your own mappings for specific response codes. For example if you wanted to map every request for something that cannot be found to the default action in the Storecontroller you could do so with the mapping shown in Listing 6-20. Listing 6-20. Custom Mapping for All 404 Response Codes class UrlMappings static mappings 404 controller store . Taking Advantage of Reverse URL Mapping You have seen how to support URLs such as showArtist Pink_Floyd instead of URLs such as artist show 42. The support you have seen so far relates to handling a request to a URL. The other end of that interaction is equally important. That is you need a slick mechanism for generating links that takes advantage of custom URL mappings. Fortunately that mechanism is built into Grails and is as easy to work with as the mapping mechanisms you have already seen. The g link GSP tag that is bundled with Grails is useful for generating links to certain controllers and actions. See Listing 6-21 for a common use of the link tag. Listing 6-21. The Link Tag td g link action show controller artist id g link td This tag will generate a link like a href artist show 42 Pink Floyd a . That link to artist show 42 is ugly. You would definitely prefer showArtist Pink_Floyd. The good news is that it is easy to get the link tag to generate a link like that. You just tell the link tag what controller and action you want to link to and supply all the necessary parameters that the custom mapping calls for. For example see the custom mapping in Listing 6-22. Listing 6-22. A Mapping for the showArtist URL class UrlMappings static mappings showArtist artistName controller artist action show . CHAPTER 6 MAPPING URLS 155 The link tag will generate a link that takes advantage of this mapping whenever a request is made for a link to the show action in the Artistcontroller and the artistName parameter is supplied. In a GSP that would look something like the code in
