應用程序框架實戰二十六:查詢對象
信息系統的查詢需求千變萬化，在倉儲中為每個查詢需求創建一個特殊方法，將導致大量乏味而臃腫的接口。
一種更加可行的辦法是，在應用層服務中描述查詢需求，并通過倉儲執行查詢。
為了能夠更好的描述查詢需求，可以將查詢功能從倉儲中抽取出來，專門創建一個查詢對象。
查詢最復雜的部分是條件過濾，這也是查詢對象的主要職責。查詢對象可以認為是規約模式的一個變種，允許查詢對象動態創建查詢條件。
在Util.Domains項目Repositories目錄中，創建查詢對象基接口IQueryBase，代碼如下。
using System;
using System.Linq.Expressions;
namespace Util.Domains.Repositories {
/// <summary>
/// 查詢對象
/// </summary>
/// <typeparam name="TEntity">實體類型</typeparam>
public interface IQueryBase<TEntity> : IPager where TEntity : class, IAggregateRoot {
/// <summary>
/// 獲取謂詞
/// </summary>
Expression<Func<TEntity, bool>> GetPredicate();
/// <summary>
/// 獲取排序
/// </summary>
string GetOrderBy();
}
}
IQueryBase接口主要用來支持將查詢對象傳入倉儲中。
在倉儲接口IRepository中增加兩個方法，代碼如下。
/// <summary>
/// 查詢
/// </summary>
/// <param name="query">查詢對象</param>
IQueryable<TEntity> Query( IQueryBase<TEntity> query );
/// <summary>
/// 分頁查詢
/// </summary>
/// <param name="query">查詢對象</param>
PagerList<TEntity> PagerQuery( IQueryBase<TEntity> query );
在倉儲類Repository中實現這兩個方法，代碼如下。
/// <summary>
/// 查詢
/// </summary>
/// <param name="query">查詢對象</param>
public IQueryable<TEntity> Query( IQueryBase<TEntity> query ) {
return FilterBy( Find(), query );
}
/// <summary>
/// 過濾
/// </summary>
protected IQueryable<TEntity> FilterBy( IQueryable<TEntity> queryable, IQueryBase<TEntity> query ) {
var predicate = query.GetPredicate();
if ( predicate == null )
return queryable;
return queryable.Where( predicate );
}
/// <summary>
/// 分頁查詢
/// </summary>
/// <param name="query">查詢對象</param>
public virtual PagerList<TEntity> PagerQuery( IQueryBase<TEntity> query ) {
return Query( query ).PagerResult( query );
}
以上代碼完成了將查詢對象傳入倉儲并獲取結果，下面開始實現查詢對象。
在Util.Datas項目Queries目錄中，創建IQuery接口，代碼如下。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Util.Domains;
using Util.Domains.Repositories;
namespace Util.Datas.Queries {
/// <summary>
/// 查詢對象
/// </summary>
/// <typeparam name="TEntity">實體類型</typeparam>
/// <typeparam name="TKey">實體標識類型</typeparam>
public interface IQuery<TEntity, TKey> : IQueryBase<TEntity> where TEntity : class,IAggregateRoot<TKey> {
/// <summary>
/// 添加謂詞,僅能添加一個條件,如果參數值為空，則忽略該條件
/// </summary>
/// <param name="predicate">謂詞</param>
/// <param name="isOr">是否使用Or連接</param>
IQuery<TEntity, TKey> Filter( Expression<Func<TEntity, bool>> predicate, bool isOr = false );
/// <summary>
/// 過濾條件
/// </summary>
/// <param name="propertyName">屬性名</param>
/// <param name="value">值</param>
/// <param name="operator">運算符</param>
IQuery<TEntity,TKey> Filter( string propertyName, object value, Operator @operator = Operator.Equal );
/// <summary>
/// 添加查詢條件
/// </summary>
/// <param name="criteria">查詢條件</param>
IQuery<TEntity,TKey> Filter( ICriteria<TEntity> criteria );
/// <summary>
/// 過濾int數值段
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
IQuery<TEntity,TKey> FilterInt<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, int? min,int? max );
/// <summary>
/// 過濾double數值段
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
IQuery<TEntity,TKey> FilterDouble<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, double? min,
double? max );
/// <summary>
/// 過濾日期段，不包含時間
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
IQuery<TEntity,TKey> FilterDate<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, DateTime? min,
DateTime? max );
/// <summary>
/// 過濾日期時間段，包含時間
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
IQuery<TEntity,TKey> FilterDateTime<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression,
DateTime? min, DateTime? max );
/// <summary>
/// 過濾decimal數值段
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
IQuery<TEntity,TKey> FilterDecimal<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, decimal? min,
decimal? max );
/// <summary>
/// 與連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="query">查詢對象</param>
IQuery<TEntity,TKey> And( IQuery<TEntity,TKey> query );
/// <summary>
/// 與連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="predicate">謂詞</param>
IQuery<TEntity,TKey> And( Expression<Func<TEntity, bool>> predicate );
/// <summary>
/// 或連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="query">查詢對象</param>
IQuery<TEntity,TKey> Or( IQuery<TEntity,TKey> query );
/// <summary>
/// 或連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="predicate">謂詞</param>
IQuery<TEntity,TKey> Or( Expression<Func<TEntity, bool>> predicate );
/// <summary>
/// 添加排序，支持多次調用OrderBy創建多級排序
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="expression">屬性表達式</param>
/// <param name="desc">是否降序</param>
IQuery<TEntity,TKey> OrderBy<TProperty>( Expression<Func<TEntity, TProperty>> expression, bool desc = false );
/// <summary>
/// 添加排序，支持多次調用OrderBy創建多級排序
/// </summary>
/// <param name="propertyName">排序屬性</param>
/// <param name="desc">是否降序</param>
IQuery<TEntity,TKey> OrderBy( string propertyName, bool desc = false );
/// <summary>
/// 獲取列表
/// </summary>
/// <param name="queryable">數據源</param>
List<TEntity> GetList( IQueryable<TEntity> queryable );
/// <summary>
/// 獲取分頁列表
/// </summary>
/// <param name="queryable">數據源</param>
PagerList<TEntity> GetPagerList( IQueryable<TEntity> queryable );
}
}
查詢對象中定義的過濾方法默認都是以And方式連接，所以需要增加專門的Or連接方法。當查詢需求比較復雜時，可以創建多個查詢對象進行合并，從而創建更為復雜的查詢條件。
為了使用方便，查詢對象本身還提供了獲取數據的方法，需要傳入IQueryable 對象，以便執行實際的查詢操作。
在Util.Datas項目Queries目錄中，創建查詢對象實現類Query，代碼如下。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Util.Datas.Queries.Criterias;
using Util.Datas.Queries.OrderBys;
using Util.Domains;
using Util.Domains.Repositories;
namespace Util.Datas.Queries {
/// <summary>
/// 查詢對象
/// </summary>
/// <typeparam name="TEntity">實體類型</typeparam>
/// <typeparam name="TKey">實體標識類型</typeparam>
public class Query<TEntity, TKey> : Pager, IQuery<TEntity, TKey> where TEntity : class ,IAggregateRoot<TKey> {
#region 構造方法
/// <summary>
/// 初始化查詢對象
/// </summary>
public Query() {
OrderBuilder = new OrderByBuilder();
}
/// <summary>
/// 初始化查詢對象
/// </summary>
/// <param name="pager">分頁對象</param>
public Query( IPager pager ) : this() {
Page = pager.Page;
PageSize = pager.PageSize;
TotalCount = pager.TotalCount;
OrderBy( pager.Order );
}
#endregion
#region 屬性
/// <summary>
/// 查詢條件
/// </summary>
private ICriteria<TEntity> Criteria { get; set; }
/// <summary>
/// 排序生成器
/// </summary>
private OrderByBuilder OrderBuilder { get; set; }
#endregion
#region GetPredicate(獲取謂詞)
/// <summary>
/// 獲取謂詞
/// </summary>
public Expression<Func<TEntity, bool>> GetPredicate() {
if ( Criteria == null )
return null;
return Criteria.GetPredicate();
}
#endregion
#region GetOrderBy(獲取排序)
/// <summary>
/// 獲取排序
/// </summary>
public string GetOrderBy() {
Order = OrderBuilder.Generate();
if ( string.IsNullOrWhiteSpace( Order ) )
Order = "Id desc";
return Order;
}
#endregion
#region 過濾條件
/// <summary>
/// 添加謂詞,僅能添加一個條件,如果參數值為空，則忽略該條件
/// </summary>
/// <param name="predicate">謂詞</param>
/// <param name="isOr">是否使用Or連接</param>
public IQuery<TEntity, TKey> Filter( Expression<Func<TEntity, bool>> predicate,bool isOr = false ) {
predicate = QueryHelper.ValidatePredicate( predicate );
if ( predicate == null )
return this;
if ( isOr )
Or( predicate );
else
And( predicate );
return this;
}
/// <summary>
/// 過濾條件
/// </summary>
/// <param name="propertyName">屬性名</param>
/// <param name="value">值</param>
/// <param name="operator">運算符</param>
public IQuery<TEntity, TKey> Filter( string propertyName, object value, Operator @operator = Operator.Equal ) {
return Filter( Lambda.ParsePredicate<TEntity>( propertyName, value, @operator ) );
}
/// <summary>
/// 添加查詢條件
/// </summary>
/// <param name="criteria">查詢條件</param>
public IQuery<TEntity, TKey> Filter( ICriteria<TEntity> criteria ) {
And( criteria.GetPredicate() );
return this;
}
/// <summary>
/// 過濾int數值段
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
public IQuery<TEntity, TKey> FilterInt<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, int? min, int? max ) {
return Filter( new IntSegmentCriteria<TEntity, TProperty>( propertyExpression, min, max ) );
}
/// <summary>
/// 過濾double數值段
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
public IQuery<TEntity, TKey> FilterDouble<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, double? min, double? max ) {
return Filter( new DoubleSegmentCriteria<TEntity, TProperty>( propertyExpression, min, max ) );
}
/// <summary>
/// 過濾日期段，不包含時間
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
public IQuery<TEntity, TKey> FilterDate<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, DateTime? min, DateTime? max ) {
return Filter( new DateSegmentCriteria<TEntity, TProperty>( propertyExpression, min, max ) );
}
/// <summary>
/// 過濾日期時間段，包含時間
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
public IQuery<TEntity, TKey> FilterDateTime<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, DateTime? min, DateTime? max ) {
return Filter( new DateTimeSegmentCriteria<TEntity, TProperty>( propertyExpression, min, max ) );
}
/// <summary>
/// 過濾decimal數值段
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="propertyExpression">屬性表達式，范例：t => t.Age</param>
/// <param name="min">最小值</param>
/// <param name="max">最大值</param>
public IQuery<TEntity, TKey> FilterDecimal<TProperty>( Expression<Func<TEntity, TProperty>> propertyExpression, decimal? min, decimal? max ) {
return Filter( new DecimalSegmentCriteria<TEntity, TProperty>( propertyExpression, min, max ) );
}
#endregion
#region 連接
/// <summary>
/// 與連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="query">查詢對象</param>
public IQuery<TEntity, TKey> And( IQuery<TEntity, TKey> query ) {
return And( query.GetPredicate() );
}
/// <summary>
/// 與連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="predicate">謂詞</param>
public IQuery<TEntity, TKey> And( Expression<Func<TEntity, bool>> predicate ) {
if ( Criteria == null ) {
Criteria = new Criteria<TEntity>( predicate );
return this;
}
Criteria = new AndCriteria<TEntity>( Criteria.GetPredicate(), predicate );
return this;
}
/// <summary>
/// 或連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="query">查詢對象</param>
public IQuery<TEntity, TKey> Or( IQuery<TEntity, TKey> query ) {
return Or( query.GetPredicate() );
}
/// <summary>
/// 或連接,將傳入的查詢條件合并到當前對象
/// </summary>
/// <param name="predicate">謂詞</param>
public IQuery<TEntity, TKey> Or( Expression<Func<TEntity, bool>> predicate ) {
if ( Criteria == null ) {
Criteria = new Criteria<TEntity>( predicate );
return this;
}
Criteria = new OrCriteria<TEntity>( Criteria.GetPredicate(), predicate );
return this;
}
#endregion
#region OrderBy(排序)
/// <summary>
/// 添加排序，支持多次調用OrderBy創建多級排序
/// </summary>
/// <typeparam name="TProperty">屬性類型</typeparam>
/// <param name="expression">屬性表達式</param>
/// <param name="desc">是否降序</param>
public IQuery<TEntity, TKey> OrderBy<TProperty>( Expression<Func<TEntity, TProperty>> expression, bool desc = false ) {
return OrderBy( Lambda.GetName( expression ), desc );
}
/// <summary>
/// 添加排序，支持多次調用OrderBy創建多級排序
/// </summary>
/// <param name="propertyName">排序屬性</param>
/// <param name="desc">是否降序</param>
public IQuery<TEntity, TKey> OrderBy( string propertyName, bool desc = false ) {
OrderBuilder.Add( propertyName, desc );
GetOrderBy();
return this;
}
#endregion
#region Clear(清理)
/// <summary>
/// 清理
/// </summary>
public void Clear() {
Criteria = null;
OrderBuilder = new OrderByBuilder();
}
#endregion
#region GetList(獲取列表)
/// <summary>
/// 獲取列表
/// </summary>
/// <param name="queryable">數據源</param>
public List<TEntity> GetList( IQueryable<TEntity> queryable ) {
return Execute( queryable ).OrderBy( Order ).ToList();
}
/// <summary>
/// 執行過濾和分頁
/// </summary>
private IQueryable<TEntity> Execute( IQueryable<TEntity> queryable ) {
queryable.CheckNull( "queryable" );
queryable = FilterBy( queryable );
GetOrderBy();
return queryable;
}
/// <summary>
/// 過濾
/// </summary>
private IQueryable<TEntity> FilterBy( IQueryable<TEntity> queryable ) {
if ( Criteria == null )
return queryable;
return queryable.Where( Criteria.GetPredicate() );
}
#endregion
#region GetPagerList(獲取分頁列表)
/// <summary>
/// 獲取分頁列表
/// </summary>
/// <param name="queryable">數據源</param>
public PagerList<TEntity> GetPagerList( IQueryable<TEntity> queryable ) {
return Execute( queryable ).PagerResult( this );
}
#endregion
}
}
應用層服務可以這樣查詢。
public PagerList<ApplicationDto> Query( ApplicationQuery query ) {
return new Query<Application>(query)
.Filter( t => t.Code == query.Code )
.Filter( t => t.Name.Contains( query.Name ) )
.Filter( t => t.Enabled == query.Enabled )
.FilterDate( t => t.CreateTime, query.BeginCreateTime, query.EndCreateTime )
.GetPagerList( Repository.Find() ).Convert( t => t.ToDto() );
}
或
public PagerList<ApplicationDto> Query2( ApplicationQuery query ) {
var queryObject = new Query<Application>( query )
.Filter( t => t.Code == query.Code )
.Filter( t => t.Name.Contains( query.Name ) )
.Filter( t => t.Enabled == query.Enabled )
.FilterDate( t => t.CreateTime, query.BeginCreateTime, query.EndCreateTime );
return Repository.PagerQuery( queryObject ).Convert( t => t.ToDto() );
}
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