Spring對(duì)靜態(tài)變量無法注入的解決方案

第Spring對(duì)靜態(tài)變量無法注入的解決方案beanid="JDBCUtils"init-method="init"

propertyname="dataSource"ref="dataSource"/property

/bean

靜態(tài)方法注入bean失敗原因

今天在寫redission的一個(gè)工具類的時(shí)候,隨手寫出下面的代碼

packagecom.wt.redission.wtredission.utils;

importorg.redisson.api.*;

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

importorg.springframework.stereotype.Component;

importjavax.annotation.PostConstruct;

@Component

publicclassRedissionUtilserror{

@Autowired

privatestaticRedissonClientredissonClient;

publicstaticRLockgetRLock(StringobjectName){

RLockrLock=redissonClient.getLock(objectName);

returnrLock;

//根據(jù)名字獲取map

publicstaticK,VRMapK,VgetRMap(StringobjectName){

RMapK,Vmap=redissonClient.getMap(objectName);

returnmap;

//根據(jù)名字和值設(shè)置map

publicstaticvoidsetMap(StringobjectName,Objectkey,Objectvalue){

RMapObject,Objectmap=redissonClient.getMap(objectName);

map.put(key,value);

//根據(jù)名字獲取set

publicstaticVRSetVgetSet(StringobjectName){

RSetVset=redissonClient.getSet(objectName);

returnset;

//根據(jù)名字和值設(shè)置set

publicstaticvoidsetSet(StringobjectName,Objectvalue){

RSetObjectset=redissonClient.getSet(objectName);

set.add(value);

//根據(jù)名字獲取list

publicstaticVRListVgetRList(StringobjectName){

RListVrList=redissonClient.getList(objectName);

returnrList;

//根據(jù)名字和值設(shè)置list

publicstaticvoidsetList(StringobjectName,intindex,Objectelement){

RListObjectobjectRList=redissonClient.getList(objectName);

objectRList.set(index,element);

//根據(jù)名字獲取bucket

publicstaticTRBucketTgetRBucket(StringobjectName){

RBucketTbucket=redissonClient.getBucket(objectName);

returnbucket;

//根據(jù)名字和值設(shè)置對(duì)應(yīng)的bucket

publicstaticTTsetBucket(StringobjectName,Stringvalue){

RBucketObjectbucket=redissonClient.getBucket(objectName);

bucket.set(value);

Tt=(T)bucket.get();//值類型由返回值確定

returnt;

}

乍一看好像沒問題我寫一個(gè)靜態(tài)方法然后在方法中使用靜態(tài)變量redissonClient,哇....,一切看得如此正常

當(dāng)我開始測(cè)試時(shí),NPE.............,我去這是怎么回事,自己在想這不科學(xué)啊,怎么會(huì)空指針,于是我開始找原因

最后發(fā)現(xiàn)是基礎(chǔ)不牢啊............，對(duì)jvm的類加載機(jī)制幾乎就沒考慮,簡(jiǎn)要說要錯(cuò)誤的原因

jvm在進(jìn)行類加載的時(shí)候,首先會(huì)加載類變量,類方法,也就是我這里被static修飾的方法,然后當(dāng)我調(diào)用靜態(tài)方法進(jìn)行使用的時(shí)候,會(huì)使用到redissionClient,注意這個(gè)redissionClient是通過autowired進(jìn)來的,關(guān)鍵問題就在這里,autowired的底層是通過構(gòu)造器和set方法注入bean的

redissionClient被static修飾并且還是一個(gè)接口在被調(diào)用的時(shí)候肯定沒有實(shí)例化

下面提供三種方式正確使用

packagecom.wt.redission.wtredission.utils;

importorg.redisson.api.*;

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

importorg.springframework.stereotype.Component;

importjava.util.List;

@Component

publicclassRedissionUtils{

privatestaticRedissonClientredissonClient;

@Autowired

publicRedissionUtils(RedissonClientredissonClient){

RedissionUtils.redissonClient=redissonClient;

publicstaticRLockgetRLock(StringobjectName){

RLockrLock=redissonClient.getLock(objectName);

returnrLock;

//根據(jù)名字獲取map

publicstaticK,VRMapK,VgetRMap(StringobjectName){

RMapK,Vmap=redissonClient.getMap(objectName);

returnmap;

//根據(jù)名字和值設(shè)置map

publicstaticvoidsetMap(StringobjectName,Objectkey,Objectvalue){

RMapObject,Objectmap=redissonClient.getMap(objectName);

map.put(key,value);

//根據(jù)名字獲取set

publicstaticVRSetVgetSet(StringobjectName){

RSetVset=redissonClient.getSet(objectName);

returnset;

//根據(jù)名字和值設(shè)置set

publicstaticvoidsetSet(StringobjectName,Objectvalue){

RSetObjectset=redissonClient.getSet(objectName);

set.add(value);

//根據(jù)名字獲取list

publicstaticVRListVgetRList(StringobjectName){

RListVrList=redissonClient.getList(objectName);

returnrList;

//根據(jù)名字和值設(shè)置list

publicstaticvoidsetList(StringobjectName,intindex,Objectelement){

RListObjectobjectRList=redissonClient.getList(objectName);

objectRList.set(index,element);

//根據(jù)名字獲取bucket

publicstaticTRBucketTgetRBucket(StringobjectName){

RBucketTbucket=redissonClient.getBucket(objectName);

returnbucket;

//根據(jù)名字和值設(shè)置對(duì)應(yīng)的bucket

publicstaticTTsetBucket(StringobjectName,Stringvalue){

RBucketObjectbucket=redissonClient.getBucket(objectName);

bucket.set(value);

Tt=(T)bucket.get();//值類型由返回值確定

returnt;

}

packagecom.wt.redission.wtredission.utils;

importorg.redisson.api.*;

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

importorg.springframework.stereotype.Component;

importjavax.annotation.PostConstruct;

@Component

publicclassRedissionUtils2{

@Autowired

RedissonClientredissonClient;

publicstaticRedissionUtils2redissionUtils;

@PostConstruct

publicvoidinit(){

redissionUtils=this;

redissionUtils.redissonClient=this.redissonClient;

publicstaticRLockgetRLock(StringobjectName){

RLockrLock=redissionUtils.redissonClient.getLock(objectName);

returnrLock;

//根據(jù)名字獲取map

publicstaticK,VRMapK,VgetRMap(StringobjectName){

RMapK,Vmap=redissionUtils.redissonClient.getMap(objectName);

returnmap;

//根據(jù)名字和值設(shè)置map

publicstaticvoidsetMap(StringobjectName,Objectkey,Objectvalue){

RMapObject,Objectmap=redissionUtils.redissonClient.getMap(objectName);

map.put(key,value);

//根據(jù)名字獲取set

publicstaticVRSetVgetSet(StringobjectName){

RSetVset=redissionUtils.redissonClient.getSet(objectName);

returnset;

//根據(jù)名字和值設(shè)置set

publicstaticvoidsetSet(StringobjectName,Objectvalue){

RSetObjectset=redissionUtils.redissonClient.getSet(objectName);

set.add(value);

//根據(jù)名字獲取list

publicstaticVRListVgetRList(StringobjectName){

RListVrList=redissionUtils.redissonClient.getList(objectName);

returnrList;

//根據(jù)名字和值設(shè)置list

publicstaticvoidsetList(StringobjectName,intindex,Objectelement){

RListObjectobjectRList=redissionUtils.redissonClient.getList(objectName);

objectRList.set(index,element);

//根據(jù)名字獲取bucket

publicstaticTRBucketTgetRBucket(StringobjectName){

RBucketTbucket=redissionUtils.redissonClient.getBucket(objectName);

returnbucket;

//根據(jù)名字和值設(shè)置對(duì)應(yīng)的bucket

publicstaticTTsetBucket(StringobjectName,Stringvalue){

RBucketObjectbucket=redissionUtils.redissonClient.getBucket(objectName);

bucket.set(value);

Tt=(T)bucket.get();//值類型由返回值確定

returnt;

}

方式三通過spring上下文獲取

packagecom.wt.redission.wtredission.utils;

importio.micrometer.core.instrument.util.StringUtils;

importorg.springframework.beans.BeansException;

importorg.springframework.beans.factory.NoSuchBeanDefinitionException;

importorg.springframework.context.ApplicationContext;

importorg.springframework.context.ApplicationContextAware;

importorg.springframework.context.annotation.Scope;

importorg.springframework.stereotype.Component;

importjavax.servlet.http.HttpServletRequest;

*SpringContext工具類.

*@author:Hohn

@Component

@Scope("singleton")

publicclassSpringUtilimplementsApplicationContextAware{

*Spring應(yīng)用上下文環(huán)境.

privatestaticApplicationContextapplicationContext;

*實(shí)現(xiàn)ApplicationContextAware接口的回調(diào)方法，設(shè)置上下文環(huán)境

*brparam:applicationContext

*@throwsBeansException

@Override

publicvoidsetApplicationContext(ApplicationContextapplicationContext)throwsBeansException{

SpringUtil.applicationContext=applicationContext;

*獲取ApplicationContext.

*brreturn:ApplicationContext

publicstaticApplicationContextgetApplicationContext(){

returnapplicationContext;

*獲取對(duì)象.

*brparam:name

*brreturn:Object一個(gè)以所給名字注冊(cè)的bean的實(shí)例

*@throwsBeansException

@SuppressWarnings("unchecked")

publicstaticTTgetBean(Stringname)throwsBeansException{

return(T)applicationContext.getBean(name);

*獲取類型為requiredType的對(duì)象.

*brparam:clz

*brreturn:

*@throwsBeansException

publicstaticTTgetBean(ClassTclz)throwsBeansException{

return(T)applicationContext.getBean(clz);

*如果BeanFactory包含一個(gè)與所給名稱匹配的bean定義，則返回true

*brparam:name

*brreturn:boolean

publicstaticbooleancontainsBean(Stringname){

returnapplicationContext.containsBean(name);

*判斷以給定名字注冊(cè)的bean定義是一個(gè)singleton還是一個(gè)prototype。

*如果與給定名字相應(yīng)的bean定義沒有被找到，將會(huì)拋出一個(gè)異常（NoSuchBeanDefinitionException）

*brparam:name

*brreturn:boolean

*@throwsNoSuchBeanDefinitionException

publicstaticbo