SonarQube常见问题修改

1.Refactor this method to reduce its Cognitive Complexity from 26 to the 15 allowed.-方法认知复杂度过高。

认知复杂性是衡量一个方法的控制流有多难理解的指标。具有高度认知复杂性的方法将难以维护。

复杂度计算规则
1. &&、|| 条件判断符号+1
2. if，else if，else，switch分支语句+1
3. for、while、do while 循环语句+1
4. catch 捕获异常语句+1
5. break、continue 终端语句+1
6. 如果if、for、while、do while、catch存在嵌套时，里层的语句相对于外层+1
7. sonar要求认知复杂度不能高于15

优化思路
1.针对if，else判断的处理，如果之后没有处理，则在if中直接返回，else无需使用  --优化表达式
2.代码中多层嵌套循环，逻辑重组，将多层循环抽取（明确执行该处代码具体需要满足的条件） --提炼函数
3.减少if，else，for，while，do while，catch关键字嵌套，可以把深层次的代码抽象成方法  --简化代码
4.如果大量使用if-else语句可以考虑用switch代替  --减少认知复杂度
5.判空等操作可以使用工具类，减少||，&&的判断使用

2.String literals should not be duplicated -字符串重复出现3次及3次以上

重复的字符串文字使重构过程容易出错，因为必须确保更新所有出现的内容。另一方面，常量可以从许多地方引用，但只需要在一个地方更新。
新加了一个常量类ConstantStr.java
// Noncompliant
public void run() {
  prepare("action1");
  execute("action1");
  release("action1");
}

// Compliant
private static final String ACTION_1 = "action1";
public void run() {
  prepare(ACTION_1);
  execute(ACTION_1);
  release(ACTION_1);
}

3.Try-with-resources should be used -优先使用Try-with-resources

try-with-resource并不是JVM虚拟机的新增功能，只是JDK实现了一个语法糖，当你将上面代码反编译后会发现，其实对JVM虚拟机而言，它依然是之前try/catch/finally的写法
// Noncompliant
FileReader fr = null;
BufferedReader br = null;
try {
  fr = new FileReader(fileName);
  br = new BufferedReader(fr);
  return br.readLine();
} catch (...) {
} finally {
  if (br != null) {
    try {
      br.close();
    } catch(IOException e){...}
  }
  if (fr != null ) {
    try {
      br.close();
    } catch(IOException e){...}
  }
}

// Compliant
try (
    FileReader fr = new FileReader(fileName);
    BufferedReader br = new BufferedReader(fr)
  ) {
  return br.readLine();
}
catch (...) {}

4.Jump statements should not occur in "finally" blocks -跳出语句不应该在finally里面

在finally代码块里return、break、throw等操作，会抑制try或catch块中抛出的任何未处理的异常传播。
// Noncompliant 
public static void doSomethingWhichThrowsException() {
  try {
    throw new RuntimeException();
  } finally {
    doSomething()
    /* ... */
    return; 
  }     
}

// Compliant
public static void doSomethingWhichThrowsException() {
  try {
    throw new RuntimeException();
  } finally {
    doSomething()
    /* ... */
  }
}
or
public void upload(File file) throws IOException {
    ChannelSftp c = (ChannelSftp) channel;
    BufferedInputStream bis = new BufferedInputStream(file.toInputStream());
    SftpException sftpException = null;
    try {
        String uploadLocation = Files.simplifyPath(this.fileLocation +"/" + file.getName());
        c.put(bis, uploadLocation);
    } catch (SftpException e) {
        sftpException = e;
        throw new IllegalTargetException("Error occurred while uploading" + e.getMessage());
    } finally {
        if (sftpException != null) {
            try {
                bis.close();
            } catch (Throwable t) {
                sftpException.addSuppressed(t);
            }
        } else {
            bis.close();
        }
    }
}

5.Constant names should comply with a naming convention -常量类型命名不符合规则

^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$
// Noncompliant 
public class MyClass {
  public static final int first = 1;
}

public enum MyEnum {
  first;
}

// Compliant
public class MyClass {
  public static final int FIRST = 1;
}

public enum MyEnum {
  FIRST;
}

6.Methods should not be empty -方法不能为空

// Noncompliant 
public void doSomething() {
}
// Compliant
public void doSomething() {
  // Do nothing because of X and Y.
  //or
  throw new UnsupportedOperationException();
}

7."String#replace" should be preferred to "String#replaceAll" -优先使用replace

replace和replaceAll效果是一样的，只不过replaceAll是正则表达式替换，效率低

8."switch" statements should have "default" clauses -switch语句要有default字句

// Compliant
public void doSomething() {
  switch (type) {
    case "0":
      return ItemTypeEnum.YZJ;
    default:
      // Do nothing because of X and Y.
      //or
      return null;
  }
}

9."@RequestMapping" methods should specify HTTP method -@RequestMapping该注解要指定HTTP方法

@RequestMapping(value = "/get/{id}", method = RequestMethod.GET)
可以简化为
@GetMapping("/get/{id}")

10.Factory method injection should be used in "@Configuration" classes -不要对有@Configuration注解的配置类进行Field级的依赖注入

在@Configuration构造的时候，需要加载依赖，但是@Configuration下面的@Bean初始化时并不是都会用到这些依赖，增加了依赖循环的风险
所以在@Bean初始化的时候用哪个依赖，去加载哪个
// Noncompliant
@Configuration
public class FooConfiguration {
  @Autowired 
  private DataSource dataSource;  

  @Bean
  public MyService myService() {
    return new MyService(this.dataSource);
  }

  @Bean
  public MyService myService() {
    return new MyService(dataSource);
  }
}

// Compliant
@Configuration
public class FooConfiguration {
  @Bean
  public MyService myService(DataSource dataSource) {
    return new MyService(dataSource);
  }
  @Bean
  public MyService myService() {
    return new MyService(dataSource);
  }
}

11."static" base class members should not be accessed via derived types -不要使用子类的名称访问父类的静态成员，容易造成混淆

// Noncompliant
public class JsonTest {
  public void test() {
    String results = "test";
    Test str = JSONObject.parseObject(results, Test.class);
  }
}
// Compliant
public class JsonTest {
  public void test() {
    String results = "test";
    Test str = JSON.parseObject(results, Test.class);
  }
}