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Function functional interface and application

2022-07-30 06:55:00 【If I don't see you tomorrow】

LambdaExpressions and functional programming interfaces

Lambda表达式是整个Java 8The most anticipated feature of the system（Java 8 新特性终极指南）,It allows us to pass a function as a method parameter into the method body or a piece of code as data,These concepts will be familiar to those with functional programming experience,很多基于JavaThe language of the virtual machine platform（Groovy、Scala…)都引入了Lambda表达式.

Arrays.asList( "a", "b", "d" ).forEach( e -> System.out.println( e ) );

How language designers can be more friendly to support existing featuresLambdaA lot of thought has been put into expressions.Hence the concept of functional interfaces,Only one single function can be declared in a functional interface.因此,它可以隐式的转换为Lambda表达式.java.lang.Runnable和java.util.concurrent.CallableJust two good examples of functional interfaces.

Lambda表达式是Java 8最大的卖点,It potentially attracts more and more developers to use this great platform and offers advanced pureJavaConcepts supported by functional programming.更多细节请参考官方文档,You can also refer to another easy-to-understand article文章.

Function 函数式接口

使用注解@FunctionalInterface标识,并且只包含一个抽象方法的接口是函数式接口.函数式接口主要分为Supplier供给型函数、Consumer消费型函数、Runnable无参无返回型函数和Function有参有返回型函数.

Function可以看作转换型函数,The form of expression is to receive a parameter,并返回一个值.Supplier、Consumer和Runnable可以看作Function的一种特殊表现形式

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Supplier供给型函数

Supplier的表现形式为不接受参数、只返回数据

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Consumer消费型函数

Consumer消费型函数和Supplier刚好相反.Consumer接收一个参数,没有返回值

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Runnable无参无返回型函数

Runnable的表现形式为即没有参数也没有返回值

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Function functional interface application

使用FunctionFunctional interface to general business encapsulation,Pass the function as a parameter when calling,The corresponding business exceptions and runtime exceptions can be encapsulated

public static <T> Result<T> of(Logger log, String interfaceName, Object params, Supplier<T> supplier) {
    
    try {
    
        return Result.success(supplier.get());
    } catch (QueryException e) {
    
        ResultCode code = ResultCode.getMessageByCode(e.getRescode());
        if (code.isLogError()) {
    
            log.error("invoke error, interfaceName:{}, params:{}, rescode:{}", interfaceName, params, e.getRescode());
        } else {
    
            log.warn("invoke error, interfaceName:{}, params:{}, rescode:{}", interfaceName, params, e.getRescode());
        }
        return Result.error(e.getRescode(), code.getMsg());
    } catch (ResultException e) {
    
        log.error("result column mapping error, interfaceName:{}, params:{}", interfaceName, params, e);
        return Result.error(ResultCode.ERROR);
    } catch (Exception e) {
    
        log.error("invoke error, interfaceName:{}, params:{}, msg:{}", interfaceName, params, e.getMessage(), e);
        return Result.error(ResultCode.SERVER_ERROR);
    }
}

函数调用

public Result<Info> getInfoById(Long id, Long num) {
    
    return SaWebdbResult.of(LOGGER, "getInfoById", Arrays.asList(id, num), () -> {
    
        Map<Long, Info> infoMap = getInfoByIdEx(Lists.newArrayList(id), num);
        return infoMap.get(id);
    });
}