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Different implementation classes of spring dynamic acquisition interface

Recently, one of the requirements of the project is to dock with the outside, get the news data from the interface, compare the data with the data in the cache, add more to the database and delete less.

There are two interfaces. At first, I wrote two methods in the business class. The code is too long. To put it simply, there are two parts:

Public Object saveANews () {/ / 1, get An interface news list / / 2, compare with cache, store data to database} public Object saveBNews () {/ / 1, get B news list / / 2, compare with cache, store data to database}

After writing, I found that because I was operating on the same table in the database, some of the code of 2 was exactly the same, only the part of 1 was different, and the part of 1 actually had only one line of code.

It has to be reused, and it's one business, and there's no need to use two separate methods, so I changed it like this:

/ / Business interface implementation method public Object saveNews (NewsUtilService service) {/ / 1, get interface news list List list = service.queryNews (); / / 2, compare with cache, store data in database} / / define news data interface public interface NewsUtilService {List queryNews ();} / two implementation classes of interface @ Servicepublic class ANewsDataServiceImpl implements NewsUtilService {@ Autowired private NewsDataMapper newsDataMapper @ Override public List queryNews () {/ / docking data}} @ Servicepublic class BNewsDataServiceImpl implements NewsUtilService {@ Override public List queryNews () {/ / docking data}} / / define factory class @ Servicepublic class NewsUtilServiceFactory {/ * * Method Name: getNewsUtilService * @ param source * @ return * / public NewsUtilService getNewsUtilService (String source) {switch (source) {case "a": return new ANewsDataServiceImpl () Case "b": return new BNewsDataServiceImpl (); default: return null;}} / / Control layer calls @ RestControllerpublic class NewsDataController {@ Resource private NewsDataService newsDataService; @ Resource private NewsUtilServiceFactory factory Public Object getNewsData () {String [] sources = {"a", "b"}; for (int I = 0; I < sources.length; iTunes +) {NewsUtilService newsUtilService = factory.getNewsUtilService (sources [I]); newsDataService.saveNews (newsUtilService);}

I thought the big job would be done, but who knew that the console reported an error after running it:

After step-by-step debugging, we finally found out what the problem was:

The Mapper injected into one of the implementation classes is not instantiated and is null.

At first, I thought it was the order of constructor calls and injections. It took me a long time to understand that it wasn't. Here's the problem:

Objects instantiated with the new keyword are not created by spring and are not managed by spring, so the annotations injected by Mapper in class An implementation classes don't work at all!

But because of the business needs, that mapper needs to be used, what should I do?

At that time, I thought of two solutions.

1. Add mapper to the method parameters of the interface and pass mapper as a parameter, but this is really strange, not to mention that the class B implementation class does not need mapper at all, and after an interface is defined, it does not care about its implementation class at all, because it seems a little strange to change the interface because of the problem of the implementation class.

So I decided to use the second, modify the factory class to look like this:

/ / define the factory class @ Servicepublic class NewsUtilServiceFactory {@ Autowired private ANewsDataServiceImpl aNewsDataServiceImpl; @ Autowired private BNewsDataServiceImpl bNewsDataServiceImpl; public NewsUtilService getNewsUtilService (String source) {switch (source) {case "a": return aNewsDataServiceImpl; case "b": return bNewsDataServiceImpl Default: return null;}

The code is speechless. First, all the implementation classes are instantiated and returned according to the input. It's not a factory mode, it's a store mode. But I couldn't think of any other way at that time, so I wrote it first, but I always thought there must be another solution. Until I was free today, I went to check it out and found that I had more low.

In fact, spring can dynamically obtain the ~ of the implementation class.

@ Servicepublic class NewsUtilServiceFactory {@ Autowired private ApplicationContext applicationContext; public NewsUtilService getNewsUtilService (String source) {switch (source) {case "web": return applicationContext.getBean (WebNewsDataServiceImpl.class) Case "oa": return applicationContext.getBean (OANewDataServiceImpl.class); default: return null;}}

This is the correct way to write it!

Finally got it out, quickly write it down.

Get all the implementation classes of an interface

In a springboot project, for convenience, we may need to get all the implementation classes under an interface and match them by name.

Text

1 、 ServiceLocator.java

Package com.yang.config;import com.yang.workOrder.service.IRootService;import org.springframework.beans.BeansException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;import org.springframework.stereotype.Component;import java.util.Map / * explain: obtain the application context and the corresponding interface implementation class * * @ author yang * @ date 2021-1-5 * / @ Componentpublic class ServiceLocator implements ApplicationContextAware {/ * used to save the interface implementation class name and the corresponding class * / private Map map / * get the application context and get the corresponding interface implementation class * @ param applicationContext * @ throws BeansException * / @ Override public void setApplicationContext (ApplicationContext applicationContext) throws BeansException {/ / return all corresponding bean map = applicationContext.getBeansOfType (IRootService.class) according to the interface type } / * get all implementation collections * @ return * / public Map getMap () {return map;} / * get the corresponding service * @ param key * @ return * / public IRootService getService (String key) {return map.get (key);}}

2 、 IRootService.java

Package com.yang.workOrder.service;import com.alibaba.fastjson.JSONObject;import com.yang.workOrder.entity.WorkOrder;/** * explain: basic process operation service interface * * @ author yang * @ date 2021-1-5 * / public interface IRootService {/ * start the process * @ param workOrder * @ return * / boolean startProcess (WorkOrder workOrder);}

3 、 RootA001ServiceImpl.java

Package com.yang.workOrder.service.impl;import com.alibaba.fastjson.JSONObject;import com.yang.workOrder.entity.WorkOrder;import com.yang.workOrder.service.IRootService;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.stereotype.Service / * * explain:A_001 process approval implementation class * * @ author yang * @ date 2021-1-5 * / @ Service ("public class RootA001ServiceImpl implements IRootService 001") public class RootA001ServiceImpl implements IRootService {private static final Logger LOGGER = LoggerFactory.getLogger (RootA001ServiceImpl.class); @ Override public boolean startProcess (WorkOrder workOrder) {return false;}}

4 、 RootA002ServiceImpl.java

Package com.yang.workOrder.service.impl;import com.alibaba.fastjson.JSONObject;import com.yang.workOrder.entity.WorkOrder;import com.yang.workOrder.service.IRootService;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.stereotype.Service / * * explain:A_002 process approval implementation class * * @ author yang * @ date 2021-1-5 * / @ Service ("Agg002") public class RootA002ServiceImpl implements IRootService {private static final Logger LOGGER = LoggerFactory.getLogger (RootA002ServiceImpl.class); @ Override public boolean startProcess (WorkOrder workOrder) {return false;}} result

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