分页
如果你的数据库中有数百万的记录，你肯定不希望将其一骨碌地给到同一个页面中。那样的话，客户端和服务端都无法承受。所以，你需要分页。
添加分页逻辑
调整方法参数，domain/gateway/book_manager.go：
@@ -12,5 +12,5 @@ type BookManager interface {
UpdateBook(ctx context.Context, id uint, b *model.Book) error
DeleteBook(ctx context.Context, id uint) error
GetBook(ctx context.Context, id uint) (*model.Book, error)
- GetBooks(ctx context.Context) ([]*model.Book, error)
+ GetBooks(ctx context.Context, offset int) ([]*model.Book, error)
}
为 GetBooks 方法添加名为 offset 的参数。
在 infrastructure/config/config.go 中添加 pageSize 配置项：
@@ -21,7 +21,8 @@ type DBConfig struct {
}
type ApplicationConfig struct {
- Port int `json:"port" yaml:"port"`
+ Port int `json:"port" yaml:"port"`
+ PageSize int `json:"page_size" yaml:"page_size"`
}
type CacheConfig struct {
设置 page_size 配置值，config.yml：
@@ -1,5 +1,6 @@
app:
port: 8080
+ page_size: 5
db:
file_name: "test.db"
合入 PageSize，application/wire_helper.go：
@@ -15,7 +15,7 @@ type WireHelper struct {
}
func NewWireHelper(c *config.Config) (*WireHelper, error) {
- db, err := database.NewMySQLPersistence(c.DB.DSN)
+ db, err := database.NewMySQLPersistence(c.DB.DSN, c.App.PageSize)
if err != nil {
return nil, err
}
更新查询逻辑，将 offset 和 pageSize 考虑进去，infrastructure/database/mysql.go：
@@ -13,10 +13,11 @@ import (
)
type MySQLPersistence struct {
- db *gorm.DB
+ db *gorm.DB
+ pageSize int
}
-func NewMySQLPersistence(dsn string) (*MySQLPersistence, error) {
+func NewMySQLPersistence(dsn string, pageSize int) (*MySQLPersistence, error) {
db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
if err != nil {
return nil, err
@@ -24,7 +25,7 @@ func NewMySQLPersistence(dsn string) (*MySQLPersistence, error) {
// Auto Migrate the data structs
db.AutoMigrate(&model.Book{})
- return &MySQLPersistence{db}, nil
+ return &MySQLPersistence{db, pageSize}, nil
}
func (s *MySQLPersistence) CreateBook(ctx context.Context, b *model.Book) (uint, error) {
@@ -54,9 +55,9 @@ func (s *MySQLPersistence) GetBook(ctx context.Context, id uint) (*model.Book, e
return &book, nil
}
-func (s *MySQLPersistence) GetBooks(ctx context.Context) ([]*model.Book, error) {
+func (s *MySQLPersistence) GetBooks(ctx context.Context, offset int) ([]*model.Book, error) {
books := make([]*model.Book, 0)
- if err := s.db.WithContext(ctx).Find(&books).Error; err != nil {
+ if err := s.db.WithContext(ctx).Offset(offset).Limit(s.pageSize).Find(&books).Error; err != nil {
return nil, err
}
return books, nil
调整缓存键，application/executor/book_operator.go：
@@ -3,6 +3,7 @@ package executor
import (
"context"
"encoding/json"
+ "fmt"
"literank.com/rest-books/domain/gateway"
"literank.com/rest-books/domain/model"
@@ -33,8 +34,9 @@ func (o *BookOperator) GetBook(ctx context.Context, id uint) (*model.Book, error
return o.bookManager.GetBook(ctx, id)
}
-func (o *BookOperator) GetBooks(ctx context.Context) ([]*model.Book, error) {
- rawValue, err := o.cacheHelper.Load(ctx, booksKey)
+func (o *BookOperator) GetBooks(ctx context.Context, offset int) ([]*model.Book, error) {
+ k := fmt.Sprintf("%s-%d", booksKey, offset)
+ rawValue, err := o.cacheHelper.Load(ctx, k)
if err != nil {
return nil, err
}
@@ -47,7 +49,7 @@ func (o *BookOperator) GetBooks(ctx context.Context) ([]*model.Book, error) {
}
} else {
// Cache key does not exist
- books, err = o.bookManager.GetBooks(ctx)
+ books, err = o.bookManager.GetBooks(ctx, offset)
if err != nil {
return nil, err
}
@@ -55,7 +57,7 @@ func (o *BookOperator) GetBooks(ctx context.Context) ([]*model.Book, error) {
if err != nil {
return nil, err
}
- if err := o.cacheHelper.Save(ctx, booksKey, string(value)); err != nil {
+ if err := o.cacheHelper.Save(ctx, k, string(value)); err != nil {
return nil, err
}
}
最后一步，在 adaptor/router.go 中传递 query 参数：
@@ -12,7 +12,10 @@ import (
"literank.com/rest-books/domain/model"
)
-const fieldID = "id"
+const (
+ fieldID = "id"
+ fieldOffset = "o"
+)
// RestHandler handles all restful requests
type RestHandler struct {
@@ -50,7 +53,17 @@ func MakeRouter(wireHelper *application.WireHelper) (*gin.Engine, error) {
// Get all books
func (r *RestHandler) getBooks(c *gin.Context) {
- books, err := r.bookOperator.GetBooks(c)
+ offset := 0
+ offsetParam := c.Query(fieldOffset)
+ if offsetParam != "" {
+ value, err := strconv.Atoi(offsetParam)
+ if err != nil {
+ c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid offset"})
+ return
+ }
+ offset = value
+ }
+ books, err := r.bookOperator.GetBooks(c, offset)
if err != nil {
fmt.Printf("Failed to get books: %v\n", err)
c.JSON(http.StatusNotFound, gin.H{"error": "failed to get books"})
好啦！改完啦！让我们试下。
使用 curl 测试
放入待测试数据
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Great Gatsby", "author": "F. Scott Fitzgerald", "published_at": "1925-04-10", "description": "A novel depicting the opulent lives of wealthy Long Island residents during the Jazz Age.", "isbn": "9780743273565", "total_pages": 218}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "To Kill a Mockingbird", "author": "Harper Lee", "published_at": "1960-07-11", "description": "A novel set in the American South during the 1930s, dealing with themes of racial injustice and moral growth.", "isbn": "9780061120084", "total_pages": 281}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "1984", "author": "George Orwell", "published_at": "1949-06-08", "description": "A dystopian novel depicting a totalitarian regime, surveillance, and propaganda.", "isbn": "9780451524935", "total_pages": 328}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "Pride and Prejudice", "author": "Jane Austen", "published_at": "1813-01-28", "description": "A classic novel exploring the themes of love, reputation, and social class in Georgian England.", "isbn": "9780486284736", "total_pages": 279}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Catcher in the Rye", "author": "J.D. Salinger", "published_at": "1951-07-16", "description": "A novel narrated by a disaffected teenager, exploring themes of alienation and identity.", "isbn": "9780316769488", "total_pages": 277}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Lord of the Rings", "author": "J.R.R. Tolkien", "published_at": "1954-07-29", "description": "A high fantasy epic following the quest to destroy the One Ring and defeat the Dark Lord Sauron.", "isbn": "9780544003415", "total_pages": 1178}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "Moby-Dick", "author": "Herman Melville", "published_at": "1851-10-18", "description": "A novel exploring themes of obsession, revenge, and the nature of good and evil.", "isbn": "9780142000083", "total_pages": 624}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Hobbit", "author": "J.R.R. Tolkien", "published_at": "1937-09-21", "description": "A fantasy novel set in Middle-earth, following the adventure of Bilbo Baggins and the quest for treasure.", "isbn": "9780345339683", "total_pages": 310}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Adventures of Huckleberry Finn", "author": "Mark Twain", "published_at": "1884-12-10", "description": "A novel depicting the journey of a young boy and an escaped slave along the Mississippi River.", "isbn": "9780486280615", "total_pages": 366}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "War and Peace", "author": "Leo Tolstoy", "published_at": "1869-01-01", "description": "A novel depicting the Napoleonic era in Russia, exploring themes of love, war, and historical determinism.", "isbn": "9781400079988", "total_pages": 1392}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "Alice’s Adventures in Wonderland", "author": "Lewis Carroll", "published_at": "1865-11-26", "description": "A children’s novel featuring a young girl named Alice who falls into a fantastical world populated by peculiar creatures.", "isbn": "9780141439761", "total_pages": 192}' http://localhost:8080/books
curl -X POST -H "Content-Type: application/json" -d '{"title": "The Odyssey", "author": "Homer", "published_at": "8th Century BC", "description": "An ancient Greek epic poem attributed to Homer, detailing the journey of Odysseus after the Trojan War.", "isbn": "9780140268867", "total_pages": 541}' http://localhost:8080/books
列出第一页的图书
curl -X GET http://localhost:8080/books
结果：
[
{
"id": 1,
"title": "Great Book II",
"author": "Carl Smith",
"published_at": "2022-01-01 08:00:00.000",
"description": "Another sample book description",
"isbn": "8334567890",
"total_pages": 3880,
"created_at": "2024-02-25T16:29:31.353+08:00",
"updated_at": "2024-02-25T16:29:31.353+08:00"
},
{
"id": 2,
"title": "The Great Gatsby",
"author": "F. Scott Fitzgerald",
"published_at": "1925-04-10",
"description": "A novel depicting the opulent lives of wealthy Long Island residents during the Jazz Age.",
"isbn": "9780743273565",
"total_pages": 218,
"created_at": "2024-02-26T17:28:26.542+08:00",
"updated_at": "2024-02-26T17:28:26.542+08:00"
},
{
"id": 3,
"title": "To Kill a Mockingbird",
"author": "Harper Lee",
"published_at": "1960-07-11",
"description": "A novel set in the American South during the 1930s, dealing with themes of racial injustice and moral growth.",
"isbn": "9780061120084",
"total_pages": 281,
"created_at": "2024-02-26T17:28:54.178+08:00",
"updated_at": "2024-02-26T17:28:54.178+08:00"
},
{
"id": 4,
"title": "1984",
"author": "George Orwell",
"published_at": "1949-06-08",
"description": "A dystopian novel depicting a totalitarian regime, surveillance, and propaganda.",
"isbn": "9780451524935",
"total_pages": 328,
"created_at": "2024-02-26T17:28:54.197+08:00",
"updated_at": "2024-02-26T17:28:54.197+08:00"
},
{
"id": 5,
"title": "Pride and Prejudice",
"author": "Jane Austen",
"published_at": "1813-01-28",
"description": "A classic novel exploring the themes of love, reputation, and social class in Georgian England.",
"isbn": "9780486284736",
"total_pages": 279,
"created_at": "2024-02-26T17:28:54.213+08:00",
"updated_at": "2024-02-26T17:28:54.213+08:00"
}
]
列出偏移之后的图书：
curl -X GET http://localhost:8080/books?o=5
结果：
[
{
"id": 6,
"title": "The Catcher in the Rye",
"author": "J.D. Salinger",
"published_at": "1951-07-16",
"description": "A novel narrated by a disaffected teenager, exploring themes of alienation and identity.",
"isbn": "9780316769488",
"total_pages": 277,
"created_at": "2024-02-26T17:28:54.23+08:00",
"updated_at": "2024-02-26T17:28:54.23+08:00"
},
{
"id": 7,
"title": "The Lord of the Rings",
"author": "J.R.R. Tolkien",
"published_at": "1954-07-29",
"description": "A high fantasy epic following the quest to destroy the One Ring and defeat the Dark Lord Sauron.",
"isbn": "9780544003415",
"total_pages": 1178,
"created_at": "2024-02-26T17:28:54.246+08:00",
"updated_at": "2024-02-26T17:28:54.246+08:00"
},
{
"id": 8,
"title": "Moby-Dick",
"author": "Herman Melville",
"published_at": "1851-10-18",
"description": "A novel exploring themes of obsession, revenge, and the nature of good and evil.",
"isbn": "9780142000083",
"total_pages": 624,
"created_at": "2024-02-26T17:28:54.262+08:00",
"updated_at": "2024-02-26T17:28:54.262+08:00"
},
{
"id": 9,
"title": "The Hobbit",
"author": "J.R.R. Tolkien",
"published_at": "1937-09-21",
"description": "A fantasy novel set in Middle-earth, following the adventure of Bilbo Baggins and the quest for treasure.",
"isbn": "9780345339683",
"total_pages": 310,
"created_at": "2024-02-26T17:28:54.278+08:00",
"updated_at": "2024-02-26T17:28:54.278+08:00"
},
{
"id": 10,
"title": "The Adventures of Huckleberry Finn",
"author": "Mark Twain",
"published_at": "1884-12-10",
"description": "A novel depicting the journey of a young boy and an escaped slave along the Mississippi River.",
"isbn": "9780486280615",
"total_pages": 366,
"created_at": "2024-02-26T17:28:54.293+08:00",
"updated_at": "2024-02-26T17:28:54.293+08:00"
}
]
列出另一个偏移后的图书：
curl -X GET http://localhost:8080/books?o=10
结果：
[
{
"id": 11,
"title": "War and Peace",
"author": "Leo Tolstoy",
"published_at": "1869-01-01",
"description": "A novel depicting the Napoleonic era in Russia, exploring themes of love, war, and historical determinism.",
"isbn": "9781400079988",
"total_pages": 1392,
"created_at": "2024-02-26T17:28:54.309+08:00",
"updated_at": "2024-02-26T17:28:54.309+08:00"
},
{
"id": 12,
"title": "The Odyssey",
"author": "Homer",
"published_at": "8th Century BC",
"description": "An ancient Greek epic poem attributed to Homer, detailing the journey of Odysseus after the Trojan War.",
"isbn": "9780140268867",
"total_pages": 541,
"created_at": "2024-02-26T17:29:22.386+08:00",
"updated_at": "2024-02-26T17:29:22.386+08:00"
},
{
"id": 13,
"title": "Alice’s Adventures in Wonderland",
"author": "Lewis Carroll",
"published_at": "1865-11-26",
"description": "A children’s novel featuring a young girl named Alice who falls into a fantastical world populated by peculiar creatures.",
"isbn": "9780141439761",
"total_pages": 192,
"created_at": "2024-02-26T17:31:55.903+08:00",
"updated_at": "2024-02-26T17:31:55.903+08:00"
}
]
看来分页功能一切正常！进展不错！
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> 此处输出代码运行结果