ID生成器代码重构问题（下）

第一轮：提升代码可读性
Main.java

package org.example;

public class Main {
    public static void main(String[] args) {
        LogTraceIdGenerator logTraceIdGenerator = new RandomIdGenerator();
        System.out.println(logTraceIdGenerator.generate());
    }

}

IdGenerator.java

package org.example;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Random;

public interface IdGenerator{
    String generate();
}
interface LogTraceIdGenerator extends IdGenerator {
}

class RandomIdGenerator implements LogTraceIdGenerator{
    private static final Logger logger = LoggerFactory.getLogger(RandomIdGenerator.class);

    public String generate(){
        String substrOfHostName = getLastfieldOfHostName();
        long currentTimeMillis = System.currentTimeMillis();
        String randomString = generateRandomAlphameric(8);
        String id = String.format("%s-%d-%s",substrOfHostName,currentTimeMillis,randomString);
        return id;
    }

    private String getLastfieldOfHostName(){
        String substrOfHostName = null;
        try{
            String hostName = InetAddress.getLocalHost().getHostName();
            String[] tokens = hostName.split("\.");
            substrOfHostName = tokens[tokens.length - 1];
            return substrOfHostName;
        }catch(UnknownHostException e){
            logger.warn("Failed to get the host name",e);
        }
        return substrOfHostName;
    }

    private String generateRandomAlphameric(int length){
        char[] randomChars = new char[length];
        int count = 0;
        Random random = new Random();
        while(count < length){
            int maxAscii = 'z';
            int randomAscii = random.nextInt(maxAscii);
            boolean isDigit = randomAscii >='0'&& randomAscii<='9';
            boolean isUppercase = randomAscii >='A'&&randomAscii<='Z';
            boolean isLowercase = randomAscii >='a' &&randomAscii <='z';
            if(isDigit || isUppercase || isLowercase){
                randomChars[count] = (char)(randomAscii);
                ++count;
            }
        }
        return new String(randomChars);
    }
}

第二轮：提升代码可测试性

package org.example;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Random;

public interface IdGenerator{
    String generate();
}
interface LogTraceIdGenerator extends IdGenerator {
}

class RandomIdGenerator implements LogTraceIdGenerator{
    private static final Logger logger = LoggerFactory.getLogger(RandomIdGenerator.class);

    public String generate(){
        String substrOfHostName = getLastfieldOfHostName();
        long currentTimeMillis = System.currentTimeMillis();
        String randomString = generateRandomAlphameric(8);
        String id = String.format("%s-%d-%s",substrOfHostName,currentTimeMillis,randomString);
        return id;
    }


    private String getLastfieldOfHostName(){
        String substrOfHostName = null;
        try{
            String hostName = InetAddress.getLocalHost().getHostName();
            substrOfHostName = getLastSubstrSplittedByDot(hostName);
        }catch(UnknownHostException e){
            logger.warn("Failed to get the host name",e);
        }
        return substrOfHostName;
    }
    @VisibleForTesting
    protected String getLastSubstrSplittedByDot(String hostName){
        String[] tokens = hostName.split("\.");
        String substrOfHostName = tokens[tokens.length-1];
        return substrOfHostName;
    }
    @VisibleForTesting
    private String generateRandomAlphameric(int length){
        char[] randomChars = new char[length];
        int count = 0;
        Random random = new Random();
        while(count < length){
            int maxAscii = 'z';
            int randomAscii = random.nextInt(maxAscii);
            boolean isDigit = randomAscii >='0'&& randomAscii<='9';
            boolean isUppercase = randomAscii >='A'&&randomAscii<='Z';
            boolean isLowercase = randomAscii >='a' &&randomAscii <='z';
            if(isDigit || isUppercase || isLowercase){
                randomChars[count] = (char)(randomAscii);
                ++count;
            }
        }
        return new String(randomChars);
    }
}

第三轮：添加单元测试

package org.example;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.*;


public class RandomIdGeneratorTest {
    @Test
    public void testGetLastSubstrSplittedByDot(){
        RandomIdGenerator idGenerator = new RandomIdGenerator();
        String actualSubstr = idGenerator.getLastSubstrSplittedByDot("field1.field2.field3");
        assertEquals("field3",actualSubstr);

        actualSubstr = idGenerator.getLastSubstrSplittedByDot("field1");
        assertEquals("field1",actualSubstr);

        actualSubstr = idGenerator.getLastSubstrSplittedByDot("field1#field2#field3");
        assertEquals("field1#field2#field3",actualSubstr);
    }

    @Test
    public void testGetLastSubstrSplittedByDot_null0rEmpty(){
        RandomIdGenerator idGenerator = new RandomIdGenerator();
        String actualSubstr = idGenerator.getLastSubstrSplittedByDot(null);
        assertNull(actualSubstr);

        actualSubstr = idGenerator.getLastSubstrSplittedByDot("");
        assertEquals("",actualSubstr);
    }

    @Test
    public void testGenerateRandomAlphameric(){
        RandomIdGenerator idGenerator = new RandomIdGenerator();
        String actualRandomString = idGenerator.generateRandomAlphameric(6);
        assertNotNull(actualRandomString);
        assertEquals(6,actualRandomString.length());
        for(char c: actualRandomString.toCharArray()){
            assertTrue(('0'<=c && c<='9') || ('a' <= c &&c<='z')||'A'<=c && c<='Z');
        }
    }

    @Test
    public void testGenerateRandomAlphameric_lengthEqualsOrLessThanZero(){
        RandomIdGenerator idGenerator = new RandomIdGenerator();
        String actualRandomString = idGenerator.generateRandomAlphameric(0);
        assertEquals("",actualRandomString);

        actualRandomString = idGenerator.generateRandomAlphameric(-1);
        assertNull(actualRandomString);
    }
}

第四轮：添加注释

package org.example;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Random;

public interface IdGenerator{
    String generate();
}
interface LogTraceIdGenerator extends IdGenerator {
}



class RandomIdGenerator implements LogTraceIdGenerator{
    private static final Logger logger = LoggerFactory.getLogger(RandomIdGenerator.class);


    
    @Override
    public String generate(){
        String substrOfHostName = getLastfieldOfHostName();
        long currentTimeMillis = System.currentTimeMillis();
        String randomString = generateRandomAlphameric(8);
        String id = String.format("%s-%d-%s",substrOfHostName,currentTimeMillis,randomString);
        return id;
    }

    
    private String getLastfieldOfHostName(){
        String substrOfHostName = null;
        try{
            String hostName = InetAddress.getLocalHost().getHostName();
            substrOfHostName = getLastSubstrSplittedByDot(hostName);
        }catch(UnknownHostException e){
            logger.warn("Failed to get the host name",e);
        }
        return substrOfHostName;
    }
    
    @VisibleForTesting
    protected String getLastSubstrSplittedByDot(String hostName){
        String[] tokens = hostName.split("\.");
        String substrOfHostName = tokens[tokens.length-1];
        return substrOfHostName;
    }
    
    @VisibleForTesting
    protected String generateRandomAlphameric(int length){
        char[] randomChars = new char[length];
        int count = 0;
        Random random = new Random();
        while(count < length){
            int maxAscii = 'z';
            int randomAscii = random.nextInt(maxAscii);
            boolean isDigit = randomAscii >='0'&& randomAscii<='9';
            boolean isUppercase = randomAscii >='A'&&randomAscii<='Z';
            boolean isLowercase = randomAscii >='a' &&randomAscii <='z';
            if(isDigit || isUppercase || isLowercase){
                randomChars[count] = (char)(randomAscii);
                ++count;
            }
        }
        return new String(randomChars);
    }
}

原链接：35 | 实战一（下）：手把手带你将ID生成器代码从“能用”重构为“好用”