支持延迟注入，解决部分场景下构造函数循环依赖的问题

Author: lvan100

bug_20210329_test.go

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package SpringCore_test
+
+import (
+	"testing"
+
+	"github.com/go-spring/spring-core"
+)
+
+type circularA struct {
+	b *circularB
+}
+
+func newCircularA(b *circularB) *circularA {
+	return &circularA{b: b}
+}
+
+type circularB struct {
+	A *circularA `autowire:",lazy"`
+}
+
+func newCircularB() *circularB {
+	return new(circularB)
+}
+
+func Test20210329(t *testing.T) {
+	for i := 0; i < 20; i++ {
+		ctx := SpringCore.NewDefaultSpringContext()
+		ctx.RegisterNameBeanFn("1", newCircularA)
+		ctx.RegisterNameBeanFn("2", newCircularB)
+		ctx.AutoWireBeans()
+	}
+}

spring-bean-assembly.go

@@ -72,11 +72,19 @@ func (s *wiringStack) path() (path string) {
 	return path[:len(path)-1]
 }
 
+type lazyField struct {
+	parent reflect.Value
+	field  string
+	v      reflect.Value
+	tag    string
+}
+
 // defaultBeanAssembly beanAssembly 的默认实现
 type defaultBeanAssembly struct {
 	springCtx   *defaultSpringContext
 	wiringStack wiringStack
 	destroys    *list.List // 具有销毁函数的 Bean 的堆栈
+	lazyFields  []lazyField
 }
 
 // newDefaultBeanAssembly defaultBeanAssembly 的构造函数
@@ -85,6 +93,7 @@ func newDefaultBeanAssembly(springContext *defaultSpringContext) *defaultBeanAss
 		springCtx:   springContext,
 		wiringStack: newWiringStack(),
 		destroys:    list.New(),
+		lazyFields:  make([]lazyField, 0),
 	}
 }
 
@@ -448,6 +457,15 @@ func (assembly *defaultBeanAssembly) wireBeanDefinition(bd beanDefinition, onlyA
 	assembly.wiringStack.popBack()
 }
 
+func lookup(tag reflect.StructTag, keys ...string) (value string, ok bool) {
+	for _, key := range keys {
+		if value, ok = tag.Lookup(key); ok {
+			return
+		}
+	}
+	return
+}
+
 // wireObjectBean 对原始对象进行注入
 func (assembly *defaultBeanAssembly) wireObjectBean(bd beanDefinition, onlyAutoWire bool) {
 	st := bd.Type()
@@ -502,14 +520,13 @@ func (assembly *defaultBeanAssembly) wireObjectBean(bd beanDefinition, onlyAutoW
 					}
 				}
 
-				// 处理 autowire 标签，autowire 与 inject 等价
-				if beanId, ok := ft.Tag.Lookup("autowire"); ok {
-					assembly.wireStructField(fv, beanId, sv, fieldName)
-				}
-
-				// 处理 inject 标签，inject 与 autowire 等价
-				if beanId, ok := ft.Tag.Lookup("inject"); ok {
-					assembly.wireStructField(fv, beanId, sv, fieldName)
+				if beanId, ok := lookup(ft.Tag, "autowire", "inject"); ok {
+					if strings.HasSuffix(beanId, ",lazy") {
+						f := lazyField{parent: sv, field: fieldName, v: fv, tag: beanId}
+						assembly.lazyFields = append(assembly.lazyFields, f)
+					} else {
+						assembly.wireStructField(fv, beanId, sv, fieldName)
+					}
 				}
 
 				// 只处理结构体类型的字段，防止递归所以不支持指针结构体字段
@@ -580,6 +597,9 @@ func (assembly *defaultBeanAssembly) wireFunctionBean(fnValue reflect.Value, fnB
 		panic(fmt.Errorf("function bean: \"%s\" return nil", bd.FileLine()))
 	}
 
+	// 把 Bean 的原始内容解出来，调试的时候更方便
+	fnBean.rBean = fnBean.rValue.Interface()
+
 	// 对函数的返回值进行自动注入
 	b := &BeanDefinition{
 		name:   bd.Name(),

spring-bean.go

@@ -234,6 +234,7 @@ type springBean interface {
 
 // objectBean 以对象形式注册的 Bean
 type objectBean struct {
+	rBean    interface{}
 	rType    reflect.Type  // 类型
 	rValue   reflect.Value // 值
 	typeName string        // 原始类型的全限定名
@@ -243,6 +244,7 @@ type objectBean struct {
 func newObjectBean(v reflect.Value) *objectBean {
 	if t := v.Type(); IsRefType(t.Kind()) {
 		return &objectBean{
+			rBean:    v.Interface(),
 			rType:    t,
 			rValue:   v,
 			typeName: TypeName(t),

spring-context-default.go

@@ -633,6 +633,12 @@ func (ctx *defaultSpringContext) AutoWireBeans() {
 	ctx.runConfigers(assembly)
 	ctx.wireBeans(assembly)
 
+	// 处理被标记为延迟注入的那些 Bean 字段
+	for _, f := range assembly.lazyFields {
+		tag := strings.TrimSuffix(f.tag, ",lazy")
+		assembly.getBeanValue(f.v, ParseSingletonTag(tag), f.parent, f.field)
+	}
+
 	ctx.sortDestroyers()
 }