js里通过eval()函数,在知道某个方法名是可以实现调用该方法,那么在java里边又怎么实现的呢?
java里边是通过反射机制来实现,代码如下:
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import java.lang.reflect.Method;
public class Test {
public static void main(String[] args) throws Exception {
String className = "com.runqianapp.ngr.alias.example.FunClass" ;
String methodName = "sayHello" ;
Class clz = Class.forName(className);
//
Object obj = clz.newInstance();
//获取方法
Method m = obj.getClass().getDeclaredMethod(methodName, String. class );
//调用方法
String result = (String) m.invoke(obj, "aaaaa" );
System.out.println(result);
}
}
class FunClass{
public String sayHello(String s){
System.out.println(s);
return "hello!" ;
}
}
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补充知识:一个controller调用根据不同业务分发不同service
在一个项目中需要写很多的controller去调用不同的service,而写一个网关可以省去写controller层的痛苦。
下面开始介绍可以分发不同service。
1.因为service在项目启动时就已全部注入到spring容器中,所以我们需要写一个工具类,可以从spring上下文(applicationContext)中获取到对应service
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@Component
public class SpringUtil implements ApplicationContextAware {
@Autowired
private static ApplicationContext applicationContext;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
if (SpringUtil.applicationContext == null ) {
SpringUtil.applicationContext = applicationContext;
}
System.out.println( "========ApplicationContext配置成功,在普通类可以通过调用SpringUtil.getAppContext()获取applicationContext对象,applicationContext=" + SpringUtil.applicationContext + "========" );
}
//获取applicationContext
public static ApplicationContext getApplicationContext() {
return applicationContext;
}
//通过name获取 Bean.
public static Object getBean(String name) {
return getApplicationContext().getBean(name);
}
//通过class获取Bean.
public static <T> T getBean(Class<T> clazz) {
return getApplicationContext().getBean(clazz);
}
//通过name,以及Clazz返回指定的Bean
public static <T> T getBean(String name, Class<T> clazz) {
return getApplicationContext().getBean(name, clazz);
}
}
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2.上面的SpringUtil我们已经可以在上下文中直接取到对于的service了,下面就开始编写controller进行请求的分发(我称之为网关)。首先我们需要先写一个抽象类,来定义service,这样接下来的sevice只需要继承这个抽象类即可(我们还可以写一些时间统计,交易流水入库等。。自我感觉很大的用处)。
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public abstract class RootService {
private Logger logger = LoggerFactory.getLogger(RootService. class );
private long beforeTime;
private long endTime;
private void before (String action) {
beforeTime = System.currentTimeMillis();
logger.info( "交易:" + action + "开始时间:" + beforeTime);
}
private void end (String action) {
endTime = System.currentTimeMillis();
long time = endTime - beforeTime;
logger.info( "交易:" + action + "结束时间:" + endTime);
logger.info( "交易:" + action + "耗时:" + time);
}
public JSONObject execute(String actionName,Map map) {
before(actionName);
JSONObject jsonObject = doNext(map);
end(actionName);
return jsonObject;
}
private JSONObject doNext(Map map) {
try {
return doAction(map);
} catch (Exception e) {
e.printStackTrace();
JSONObject js = new JSONObject();
js.put( "retCode" , "000000" );
js.put( "retMsg" , "程序报错" );
return js;
}
}
protected abstract JSONObject doAction(Map map);
}
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3.一切准备就绪,我们可以开始编写contrconoller了(网关)
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@Controller
@RequestMapping ( "/root" )
public class RootController {
@ResponseBody
@RequestMapping (value = "/h5.do" ,produces = { "application/json;charset=UTF-8" },method = RequestMethod.POST)
public JSONObject root( @RequestBody Map<String,Object> map, HttpServletRequest httpServletRequest){
String service = (String) map.get( "service" );
JSONObject js = new JSONObject();
RootService rootService = (RootService) SpringUtil.getBean(service);
return rootService.execute(service,map);
}
}
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到这里一个网关就写好了,然后我们写一个service进行测试一下(对应的Dao层我就不现丑了,相信大家都会)
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@Service
public class UserServiceImpl extends RootService{
private Logger logger = LoggerFactory.getLogger(UserService. class );
@Autowired
private UserDao userDao;
@Override
protected JSONObject doAction(Map map) {
JSONObject js = new JSONObject();
String id = (String) map.get( "id" );
User user = userDao.getUser(id);
js.put( "user" ,user);
logger.info( "进入了UserService" );
return js;
}
}
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下面我们用postman测试一下测试报文为:
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{
"id" : "1" ,
"service" : "userServiceImpl"
}
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控制台打印为:
2019-10-18 17:24:41.089 INFO 6452 --- [nio-8080-exec-2] c.s.s.service.util.RootService : 交易:userService开始时间:1571390681089
2019-10-18 17:24:41.138 INFO 6452 --- [nio-8080-exec-2] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2019-10-18 17:24:41.227 INFO 6452 --- [nio-8080-exec-2] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
2019-10-18 17:24:41.255 INFO 6452 --- [nio-8080-exec-2] c.s.s.service.impl.UserService : 进入了UserService
2019-10-18 17:24:41.256 INFO 6452 --- [nio-8080-exec-2] c.s.s.service.util.RootService : 交易:userService结束时间:1571390681256
2019-10-18 17:24:41.256 INFO 6452 --- [nio-8080-exec-2] c.s.s.service.util.RootService : 交易:userService耗时:167
返回为:
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{
"user" : {
"user_id" : "1" ,
"password" : "123456" ,
"user_name" : "张三"
}
}
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总结:这样写法的好处在于 1.有一个统一的入口,不需要在编写controller, 可以专注于业务(service)2.可以在公共入口做公共处理。
以上这篇在java中由类名和方法名字符串实现其调用方式就是小编分享给大家的全部内容了,希望能给大家一个参考,也希望大家多多支持服务器之家。
原文链接:https://www.cnblogs.com/chen-lhx/p/5853957.html