springboot源码学习--设计模式及工具类

不念不忘少年蓝@ 2023-05-30 03:49 15阅读 0赞

## 单例模式-ApplicationConversionService ##

private static volatile ApplicationConversionService sharedInstance;
    
    public static ConversionService getSharedInstance() {
    		ApplicationConversionService sharedInstance = ApplicationConversionService.sharedInstance;
    		if (sharedInstance == null) {
    			synchronized (ApplicationConversionService.class) {
    				sharedInstance = ApplicationConversionService.sharedInstance;
    				if (sharedInstance == null) {
    					sharedInstance = new ApplicationConversionService();
    					ApplicationConversionService.sharedInstance = sharedInstance;
    				}
    			}
    		}
    		return sharedInstance;
    	}

## StringUtils(org.springframework.util.StringUtils) ##

去除空格

public static String trimAllWhitespace(String str) {
    		if (!hasLength(str)) {
    			return str;
    		}
    
    		int len = str.length();
    		StringBuilder sb = new StringBuilder(str.length());
    		for (int i = 0; i < len; i++) {
    			char c = str.charAt(i);
    			if (!Character.isWhitespace(c)) {
    				sb.append(c);
    			}
    		}
    		return sb.toString();
    	}
    	
    public static boolean hasLength(@Nullable String str) {
    		return (str != null && !str.isEmpty());
    	}

字符串转数组

public static String[] commaDelimitedListToStringArray(@Nullable String str) {
    		return delimitedListToStringArray(str, ",");
    	}
    	
    public static String[] delimitedListToStringArray(@Nullable String str, @Nullable String delimiter) {
    		return delimitedListToStringArray(str, delimiter, null);
    	}
    	
    public static String[] delimitedListToStringArray(
    			@Nullable String str, @Nullable String delimiter, @Nullable String charsToDelete) {
    
    		if (str == null) {
    			return new String[0];
    		}
    		if (delimiter == null) {
    			return new String[] {str};
    		}
    
    		List<String> result = new ArrayList<>();
    		if (delimiter.isEmpty()) {
    			for (int i = 0; i < str.length(); i++) {
    				result.add(deleteAny(str.substring(i, i + 1), charsToDelete));
    			}
    		}
    		else {
    			int pos = 0;
    			int delPos;
    			while ((delPos = str.indexOf(delimiter, pos)) != -1) {
    				result.add(deleteAny(str.substring(pos, delPos), charsToDelete));
    				pos = delPos + delimiter.length();
    			}
    			if (str.length() > 0 && pos <= str.length()) {
    				// Add rest of String, but not in case of empty input.
    				result.add(deleteAny(str.substring(pos), charsToDelete));
    			}
    		}
    		return toStringArray(result);
    }

## 双亲加载 ##

java.lang public abstract class ClassLoader
    protected Class<?> loadClass(String name, boolean resolve)
            throws ClassNotFoundException
        {
            synchronized (getClassLoadingLock(name)) {
                // First, check if the class has already been loaded
                Class<?> c = findLoadedClass(name);
                if (c == null) {
                    long t0 = System.nanoTime();
                    try {
                        if (parent != null) {
                            c = parent.loadClass(name, false);
                        } else {
                            c = findBootstrapClassOrNull(name);
                        }
                    } catch (ClassNotFoundException e) {
                        // ClassNotFoundException thrown if class not found
                        // from the non-null parent class loader
                    }
    
                    if (c == null) {
                        // If still not found, then invoke findClass in order
                        // to find the class.
                        long t1 = System.nanoTime();
                        c = findClass(name);
    
                        // this is the defining class loader; record the stats
                        sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);
                        sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
                        sun.misc.PerfCounter.getFindClasses().increment();
                    }
                }
                if (resolve) {
                    resolveClass(c);
                }
                return c;
            }
        }
     private Class<?> findBootstrapClassOrNull(String name)
        {
            if (!checkName(name)) return null;
    
            return findBootstrapClass(name);
        }
     // return null if not found
    private native Class<?> findBootstrapClass(String name);