文章以efcore 2.0.0-preview2.测试验证通过。其他版本不保证使用,但是思路不会差太远。源代码,报道越短,事情越严重!文章越短,内容越精悍!
目标:
1.实现entity的自动发现和mapper设置.
2.默认字符串长度,而不是nvarchar(max).
3.decimal设置精度
实现目标1:继承RelationalModelCustomizer,重写Customize方法。
当然,我们也可以重写dbcontext的OnModelCreating方法,but,我们怎么能这么low呢。必须要用点高级玩意是吧,当然这也是更底层的扩展方式。项目里面有多个dbcontext的话,在这里集中扩展管理比较方便。
在然后,这个RelationalModelCustomizer继承自ModelCustomizer。在联想到efcore未来的版本会支持redis,nosql什么的。到时候估计还回有一个osqlModelCustomizer之类的吧,期待中......
实现目标2、3:继承自CoreConventionSetBuilder类,重写CreateConventionSet方法。
重写CreateConventionSet方法,能拿到关键的ConventionSet对象。这个对象囊括了诸多的约定配置等等。比如maxlengthattribute属性标记,stringlength属性标记,timestamp属性标记,表id的自动发现规则等等等。。。
那,我们增加2个小小的约定:字符串默认长度(StringDefaultLengthConvention),和decimal精度设置attribute(DecimalPrecisionAttributeConvention)及fluntapi方式.
文章的最后附efcore 所有的可替换扩展service。
//servie,DI注入替换.services.AddSingleton<IModelCustomizer, MyRelationalModelCustomizer>(); services.AddSingleton<ICoreConventionSetBuilder, MyCoreConventionSetBuilder>();//实现entity的自动发现和mapper设置public class MyRelationalModelCustomizer : RelationalModelCustomizer{ public MyRelationalModelCustomizer(ModelCustomizerDependencies dependencies) : base(dependencies){} public override void Customize(ModelBuilder modelBuilder, DbContext dbContext) { base.Customize(modelBuilder, dbContext); var sp = (IInfrastructure<IServiceProvider>)dbContext; var dbOptions = sp.Instance.GetServices<DbContextOptions>(); foreach (var item in dbOptions) { if (item.ContextType == dbContext.GetType()) ConfigureDbContextEntityService.Configure(modelBuilder, item, dbContext); } } }public class MyCoreConventionSetBuilder : CoreConventionSetBuilder{ public MyCoreConventionSetBuilder(CoreConventionSetBuilderDependencies dependencies) : base(dependencies){} public override ConventionSet CreateConventionSet() { var conventionSet = base.CreateConventionSet(); //默认字符串长度,而不是nvarchar(max). //为什么要insert(0,obj),则是因为这个默认规则要最优先处理,如果后续有规则的话就直接覆盖了。 //propertyBuilder.HasMaxLength(32, ConfigurationSource.Convention); //理论上我指定了规则的级别为.Convention,应该和顺序就没有关系了。but,还没有完成测试,所以我也不知道 conventionSet.PropertyAddedConventions.Insert(0, new StringDefaultLengthConvention()); //decimal设置精度 conventionSet.PropertyAddedConventions.Add(new DecimalPrecisionAttributeConvention()); return conventionSet; } }
下面是StringDefaultLengthConvention和DecimalPrecisionAttributeConvention的实现代码
//字符串默认长度public class StringDefaultLengthConvention : IPropertyAddedConvention { public InternalPropertyBuilder Apply(InternalPropertyBuilder propertyBuilder) { if (propertyBuilder.Metadata.ClrType == typeof(string)) propertyBuilder.HasMaxLength(32, ConfigurationSource.Convention); return propertyBuilder; } }//attribute方式设置decimal精度public class DecimalPrecisionAttributeConvention : PropertyAttributeConvention<DecimalPrecisionAttribute> { public override InternalPropertyBuilder Apply(InternalPropertyBuilder propertyBuilder, DecimalPrecisionAttribute attribute, MemberInfo clrMember) { if (propertyBuilder.Metadata.ClrType == typeof(decimal)) propertyBuilder.HasPrecision(attribute.Precision, attribute.Scale); return propertyBuilder; }/// <summary>/// decimal类型设置精度/// </summary>/// <param name="propertyBuilder"></param>/// <param name="precision">精度</param>/// <param name="scale">小数位数</param>public static PropertyBuilder<TProperty> HasPrecision<TProperty>(this PropertyBuilder<TProperty> propertyBuilder, int precision = 18, int scale = 4) { //fluntapi方式设置精度 ((IInfrastructure<InternalPropertyBuilder>)propertyBuilder).Instance.HasPrecision(precision, scale); return propertyBuilder; }public static InternalPropertyBuilder HasPrecision(this InternalPropertyBuilder propertyBuilder, int precision, int scale){ propertyBuilder.Relational(ConfigurationSource.Explicit).HasColumnType($"decimal({precision},{scale})"); return propertyBuilder; }
以上就是实现的代码,就这么几行。嗯,还是挺简单的.
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以下,则是efcore的源代码。展示了如此之多的可扩展。随着DI的运用和微软的开放,嗯。用烂啦,用炸拉(^_^)
//各种规则和约定public virtual ConventionSet AddConventions(ConventionSet conventionSet){ ValueGeneratorConvention valueGeneratorConvention = new RelationalValueGeneratorConvention(); ReplaceConvention(conventionSet.BaseEntityTypeChangedConventions, valueGeneratorConvention); ReplaceConvention(conventionSet.PrimaryKeyChangedConventions, valueGeneratorConvention); ReplaceConvention(conventionSet.ForeignKeyAddedConventions, valueGeneratorConvention); ReplaceConvention(conventionSet.ForeignKeyRemovedConventions, valueGeneratorConvention); var relationalColumnAttributeConvention = new RelationalColumnAttributeConvention(); conventionSet.PropertyAddedConventions.Add(relationalColumnAttributeConvention); var sharedTableConvention = new SharedTableConvention(); conventionSet.EntityTypeAddedConventions.Add(new RelationalTableAttributeConvention()); conventionSet.EntityTypeAddedConventions.Add(sharedTableConvention); conventionSet.BaseEntityTypeChangedConventions.Add(new DiscriminatorConvention()); conventionSet.BaseEntityTypeChangedConventions.Add( new TableNameFromDbSetConvention(Dependencies.Context?.Context, Dependencies.SetFinder)); conventionSet.EntityTypeAnnotationChangedConventions.Add(sharedTableConvention); conventionSet.PropertyFieldChangedConventions.Add(relationalColumnAttributeConvention); conventionSet.PropertyAnnotationChangedConventions.Add((RelationalValueGeneratorConvention)valueGeneratorConvention); conventionSet.ForeignKeyUniquenessChangedConventions.Add(sharedTableConvention); conventionSet.ForeignKeyOwnershipChangedConventions.Add(sharedTableConvention); conventionSet.ModelBuiltConventions.Add(new RelationalTypeMappingConvention(Dependencies.TypeMapper)); conventionSet.ModelBuiltConventions.Add(sharedTableConvention); conventionSet.ModelAnnotationChangedConventions.Add(new RelationalDbFunctionConvention()); return conventionSet; }
//还是各种规则和约定public virtual ConventionSet CreateConventionSet(){ var conventionSet = new ConventionSet(); var propertyDiscoveryConvention = new PropertyDiscoveryConvention(Dependencies.TypeMapper); var keyDiscoveryConvention = new KeyDiscoveryConvention(); var inversePropertyAttributeConvention = new InversePropertyAttributeConvention(Dependencies.TypeMapper); var relationshipDiscoveryConvention = new RelationshipDiscoveryConvention(Dependencies.TypeMapper); conventionSet.EntityTypeAddedConventions.Add(new NotMappedEntityTypeAttributeConvention()); conventionSet.EntityTypeAddedConventions.Add(new NotMappedMemberAttributeConvention()); conventionSet.EntityTypeAddedConventions.Add(new BaseTypeDiscoveryConvention()); conventionSet.EntityTypeAddedConventions.Add(propertyDiscoveryConvention); conventionSet.EntityTypeAddedConventions.Add(keyDiscoveryConvention); conventionSet.EntityTypeAddedConventions.Add(inversePropertyAttributeConvention); conventionSet.EntityTypeAddedConventions.Add(relationshipDiscoveryConvention); conventionSet.EntityTypeAddedConventions.Add(new DerivedTypeDiscoveryConvention()); conventionSet.EntityTypeIgnoredConventions.Add(inversePropertyAttributeConvention); var foreignKeyIndexConvention = new ForeignKeyIndexConvention(); var valueGeneratorConvention = new ValueGeneratorConvention(); conventionSet.BaseEntityTypeChangedConventions.Add(propertyDiscoveryConvention); conventionSet.BaseEntityTypeChangedConventions.Add(keyDiscoveryConvention); conventionSet.BaseEntityTypeChangedConventions.Add(inversePropertyAttributeConvention); conventionSet.BaseEntityTypeChangedConventions.Add(relationshipDiscoveryConvention); conventionSet.BaseEntityTypeChangedConventions.Add(foreignKeyIndexConvention); conventionSet.BaseEntityTypeChangedConventions.Add(valueGeneratorConvention ); // An ambiguity might have been resolved conventionSet.EntityTypeMemberIgnoredConventions.Add(inversePropertyAttributeConvention); conventionSet.EntityTypeMemberIgnoredConventions.Add(relationshipDiscoveryConvention); var keyAttributeConvention = new KeyAttributeConvention(); var foreignKeyPropertyDiscoveryConvention = new ForeignKeyPropertyDiscoveryConvention(); var backingFieldConvention = new BackingFieldConvention(); var concurrencyCheckAttributeConvention = new ConcurrencyCheckAttributeConvention(); var databaseGeneratedAttributeConvention = new DatabaseGeneratedAttributeConvention(); var requiredPropertyAttributeConvention = new RequiredPropertyAttributeConvention(); var maxLengthAttributeConvention = new MaxLengthAttributeConvention(); var stringLengthAttributeConvention = new StringLengthAttributeConvention(); var timestampAttributeConvention = new TimestampAttributeConvention(); conventionSet.PropertyAddedConventions.Add(backingFieldConvention); conventionSet.PropertyAddedConventions.Add(concurrencyCheckAttributeConvention); conventionSet.PropertyAddedConventions.Add(databaseGeneratedAttributeConvention); conventionSet.PropertyAddedConventions.Add(requiredPropertyAttributeConvention); conventionSet.PropertyAddedConventions.Add(maxLengthAttributeConvention); conventionSet.PropertyAddedConventions.Add(stringLengthAttributeConvention); conventionSet.PropertyAddedConventions.Add(timestampAttributeConvention); conventionSet.PropertyAddedConventions.Add(keyDiscoveryConvention); conventionSet.PropertyAddedConventions.Add(foreignKeyPropertyDiscoveryConvention); conventionSet.PropertyAddedConventions.Add(keyAttributeConvention); conventionSet.PrimaryKeyChangedConventions.Add(valueGeneratorConvention); conventionSet.KeyAddedConventions.Add(foreignKeyPropertyDiscoveryConventi
http://www.cnblogs.com/calvinK/p/7234872.html