第Spring循環(huán)依賴的解決方案詳解目錄簡介方案1.Feild注入單例（@AutoWired）方案2.構(gòu)造器注入+@Lazy方案3.Setter/Field注入單例方案4.@PostConstruct方案5.實(shí)現(xiàn)ApplicationContextAware與InitializingBean

簡介

說明

本文用實(shí)例介紹如何解決Spring的循環(huán)依賴問題。

相關(guān)網(wǎng)址

Spring循環(huán)依賴之問題復(fù)現(xiàn)詳解

公共代碼

packagecom.example.controller;

importcom.example.tmp.A;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.web.bind.annotation.GetMapping;

importorg.springframework.web.bind.annotation.RestController;

@RestController

publicclassHelloController{

@Autowired

privateAa;

@GetMapping("/test1")

publicStringtest1(){

returna.getTest();

方案1.Feild注入單例（@AutoWired）

代碼

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

@Component

publicclassA{

@Autowired

privateBb;

privateStringname="Tony";

publicStringgetName(){

returnname;

publicvoidsetName(Stringname){

=name;

publicStringgetTest(){

returnb.getAge().toString()+name;

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

@Component

publicclassB{

@Autowired

privateAa;

privateIntegerage=20;

publicIntegergetAge(){

returnage;

publicvoidsetAge(Integerage){

this.age=age;

測試

啟動不報錯。

postman訪問：http://localhost:8080/test1

后端結(jié)果：不報錯

postman結(jié)果:20Tony

方案2.構(gòu)造器注入+@Lazy

延遲加載：在注入依賴時，先注入代理對象，當(dāng)首次使用時再創(chuàng)建對象完成注入。

代碼

packagecom.example.tmp;

importorg.springframework.context.annotation.Lazy;

importorg.springframework.stereotype.Component;

@Component

publicclassA{

privateBb;

publicA(@LazyBb){

this.b=b;

privateStringname="Tony";

publicStringgetName(){

returnname;

publicvoidsetName(Stringname){

=name;

publicStringgetTest(){

returnb.getAge().toString()+name;

packagecom.example.tmp;

importorg.springframework.context.annotation.Lazy;

importorg.springframework.stereotype.Component;

@Component

publicclassB{

privateAa;

publicB(@LazyAa){

this.a=a;

privateIntegerage=20;

publicIntegergetAge(){

returnage;

publicvoidsetAge(Integerage){

this.age=age;

測試

啟動不報錯。

postman訪問：http://localhost:8080/test1

后端結(jié)果：不報錯

postman結(jié)果:20Tony

方案3.Setter/Field注入單例

代碼

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

@Component

publicclassA{

privateBb;

privateStringname="Tony";

publicStringgetName(){

returnname;

publicvoidsetName(Stringname){

=name;

publicStringgetTest(){

returnb.getAge().toString()+name;

publicBgetB(){

returnb;

@Autowired

publicvoidsetB(Bb){

this.b=b;

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

@Component

publicclassB{

privateAa;

privateIntegerage=20;

publicIntegergetAge(){

returnage;

publicvoidsetAge(Integerage){

this.age=age;

publicAgetA(){

returna;

@Autowired

publicvoidsetA(Aa){

this.a=a;

測試

啟動不報錯。

postman訪問：http://localhost:8080/test1

后端結(jié)果：不報錯

postman結(jié)果:20Tony

方案4.@PostConstruct

代碼

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

importjavax.annotation.PostConstruct;

@Component

publicclassA{

@Autowired

privateBb;

@PostConstruct

publicvoidinit(){

b.setA(this);

privateStringname="Tony";

publicStringgetName(){

returnname;

publicvoidsetName(Stringname){

=name;

publicStringgetTest(){

returnb.getAge().toString()+name;

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

@Component

publicclassB{

@Autowired

privateAa;

privateIntegerage=20;

publicIntegergetAge(){

returnage;

publicvoidsetAge(Integerage){

this.age=age;

publicAgetA(){

returna;

publicvoidsetA(Aa){

this.a=a;

測試

啟動不報錯。

postman訪問：http://localhost:8080/test1

后端結(jié)果：不報錯

postman結(jié)果:20Tony

方案5.實(shí)現(xiàn)ApplicationContextAware與InitializingBean

代碼

packagecom.example.tmp;

importorg.springframework.beans.BeansException;

importorg.springframework.beans.factory.InitializingBean;

importorg.springframework.context.ApplicationContext;

importorg.springframework.context.ApplicationContextAware;

importorg.springframework.stereotype.Component;

@Component

publicclassAimplementsApplicationContextAware,InitializingBean{

privateBb;

privateApplicationContextcontext;

privateStringname="Tony";

publicStringgetName(){

returnname;

publicvoidsetName(Stringname){

=name;

publicStringgetTest(){

returnb.getAge().toString()+name;

@Override

publicvoidafterPropertiesSet()throwsException{

this.b=context.getBean(B.class);

@Override

publicvoidsetApplicationContext(ApplicationContextapplicationContext)throwsBeansException{

this.context=applicationContext;

packagecom.example.tmp;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

@Component

publicclassB{

@Autowired

priva