主要运用java反射原理，格式化输出java对象属性值，特别是list 和map。

MyTestUtil.java

package utils; import java.lang.reflect.Field; import java.text.SimpleDateFormat; import java.util.Arrays; import java.util.Collection; import java.util.Date; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; /** * 这个类是方便控制台输出object，主要应用java反射机制。 因为考虑到使用性和美观性，没有使用无限递归。 * 而是在toStr方法中加入一个boolean recursion ，是否递归。 * 当然我们也可以将boolean recursion换成int recursion，控制递归次数。 * 其实就我使用经验来看，复杂数据toString，用json工具转化成json输出是一个不错的方式。 //这是我用的方式，boolean recursion是否递归 public static int add(int i,boolean recursion){ sum+=i; if(recursion) add(i, false); return sum; } //也可以这样，int recursion表示递归次数 public static int add(int i,int recursion){ sum+=i; if(recursion>0){ recursion--; add(i, recursion); } return sum; } * * * @author klguang * */ public class MyTestUtil { static final String SPLIT_LINE = "=";// 分割线 static final String MY_SIGN = "KLG_print";//默認標記 private static String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss"; /** * 将集合类型toSring方法 * @param object * @param recursion * 是否递归 * @return */ private static String collectionToStr(Object object, boolean recursion) { if (object == null) return "null"; Object[] a = null; // 将集合类型转换成数组类型 if (isArrayType(object)) a = (Object[]) object; else a = ((Collection) object).toArray(); if (isSimpleArr(a) || !recursion) return Arrays.toString(a); else return complexArrToStr(a); } /** * Arrays有toString方法，但是对象内容太多，在一行显示 还有就是没有显示index信息 */ private static String complexArrToStr(Object[] a) { if (a == null) return "null"; int iMax = a.length - 1; if (iMax == -1) return "[]"; StringBuilder b = new StringBuilder(); for (int i = 0;; i++) { String value = objToStr(a[i], false); b.append("[" + i + "]" + " -> " + value); if (i == iMax) return b.toString(); b.append(", rn"); } } /** * map类型toString方法 * * @param map * @param recursion * 是否递归 * @return */ private static String mapToStr(Map<String, Object> map, boolean recursion) { if (map == null) return "null"; if (isSimpleMap(map) || !recursion) return simpleMapToStr(map); else return complexMapToStr(map, true); } /** * map的value是简单类型的，复制Map.toString，我给它加了换行10个换行 * * @param map * @return */ private static String simpleMapToStr(Map map) { Iterator<Entry<String, Object>> i = map.entrySet().iterator(); if (!i.hasNext()) return "{}"; StringBuilder sb = new StringBuilder(); sb.append('{'); for (int t = 1;; t++) { Entry<String, Object> e = i.next(); sb.append(e.getKey()).append(" = ").append(e.getValue()); if (!i.hasNext()) return sb.append('}').toString(); sb.append(',').append(' '); if (t % 10 == 0 && t != 0) sb.append("rn "); } } private static String complexMapToStr(Map map, boolean recursion) { Iterator<Entry<String, Object>> i = map.entrySet().iterator(); if (!i.hasNext()) return "{}"; StringBuilder sb = new StringBuilder(); sb.append("{rn"); for (int t = 1;; t++) { Entry<String, Object> e = i.next(); String key = String.valueOf(e.getKey()); Object value = e.getValue(); sb.append(indent(2," ")).append(key).append(" = "); if (isSimpleType(value) || !recursion) sb.append(String.valueOf(value)); else sb.append(objToStr(value, false)); if (!i.hasNext()) return sb.append("rn}").toString(); sb.append(',').append("rn"); } } /** * * * @param object * @param recursion * 是否要递归 * @return */ private static String beanToStr(Object object, boolean recursion) { if (object == null) return "null"; Class clazz = object.getClass(); StringBuilder sb = new StringBuilder(); //返回源代码中给出的底层类的简称 sb.append(clazz.getSimpleName()).append("["); Field[] fields = sortFieldByType(clazz.getDeclaredFields()); int iMax = fields.length - 1; if (iMax == -1) return sb.append("]").toString(); for (int i = 0;; i++) { Field field = fields[i]; field.setAccessible(true);// 设置些属性是可以访问的 String name = field.getName();// 取得field的名称 if (name.equals("serialVersionUID")) continue; try { Object value = field.get(object);// 得到此属性的值 if (isSimpleType(value) || !recursion) sb.append(name + " = " + String.valueOf(value)); else sb.append("rn" + indent(clazz.getSimpleName().length() + 2," ") + objToStr(value, false) + "rn"); } catch (Exception e) { e.printStackTrace(); } if (i == iMax) return sb.append("]").toString(); sb.append(","); } } private static String indent(int length,String sign) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < length; i++) { sb.append(sign); } return sb.toString(); } private static boolean isSimpleType(Object obj) { if (obj == null) return true; else { Class objectClass = obj.getClass(); return isSimpleType(objectClass); } } /** * * @param objectClass * 用obj.getClass()取得 * @return */ private static boolean isSimpleType(Class objectClass) { if (objectClass == boolean.class || objectClass == Boolean.class || objectClass == short.class || objectClass == Short.class || objectClass == byte.class || objectClass == Byte.class || objectClass == int.class || objectClass == Integer.class || objectClass == long.class || objectClass == Long.class || objectClass == float.class || objectClass == Float.class || objectClass == char.class || objectClass == Character.class || objectClass == double.class || objectClass == Double.class || objectClass == String.class) { return true; } else { return false; } } /** * Method isCollectionType * * @param obj * Object * @return boolean */ private static boolean isCollectionType(Object obj) { if (obj == null) return false; return (obj.getClass().isArray() || (obj instanceof Collection)); } private static boolean isArrayType(Object obj) { if (obj == null) return false; return (obj.getClass().isArray()); } private static boolean isMapType(Object obj) { if (obj == null) return false; return (obj instanceof Map); } private static boolean isDateType(Object obj){ if(obj==null) return false; return (obj instanceof Date); } private static boolean isBeanType(Object obj) { if (isSimpleType(obj) || isCollectionType(obj) || isMapType(obj)) return false; else return true; } private static boolean isSimpleArr(Object[] a) { if (a == null || a.length < 1) return true; boolean flag = true; for (Object o : a) { if (!isSimpleType(o)) { flag = false; break; } } return flag; } private static boolean isSimpleMap(Map map) { if (map == null) return true; Iterator<Entry<String, Object>> i = map.entrySet().iterator(); boolean flag = true; while (i.hasNext()) { Entry<String, Object> e = i.next(); if (!isSimpleType(e.getValue())) { flag = false; break; } } return flag; } /*** * 将简单类型排在前面 * @param fields * @return */ public static Field[] sortFieldByType(Field[] fields) { for (int i = 0; i < fields.length; i++) { if (isSimpleType(fields[i].getType())) continue;// fields[i]是简单类型不管 // fields[i]是复杂类型 // int j = i+1，从fields[i]之后开始比较 for (int j = i + 1; j < fields.length; j++) { Field fieldTmp = null; if (isSimpleType(fields[j].getType())) {// 与后面的第一个简单类型交互 fieldTmp = fields[i]; fields[i] = fields[j]; fields[j] = fieldTmp; break; // 后面的循环，是没有意义de } } } return fields; } /** * 这个方法是递归方法，并且并多个地方调用，考虑到循环引用和显示格式， boolean recursion取得确保递归可以被终止。 * * @param object * @param recursion * 是否需要更深一层显示 * @return */ private static String objToStr(Object object, boolean recursion) { if (object == null) return "null"; object.toString(); if(isDateType(object)) return new SimpleDateFormat(DATE_FORMAT).format((Date)object); else if (isBeanType(object)) return beanToStr(object, recursion); else if (isCollectionType(object)) return collectionToStr(object, recursion); else if (isMapType(object)) return mapToStr((Map) object, recursion); else return String.valueOf(object); } public static String objToStr(Object obj) { return objToStr(obj, true); } private static void print(Object obj,String sign,String content) { String begin=indent(15, SPLIT_LINE) + " " +obj.getClass().getSimpleName() + " >> " + sign + " " + indent(10, SPLIT_LINE); int length=(begin.length()-sign.length()-5)/2; String end=indent(length, SPLIT_LINE)+ " " + sign + " " + indent(length, SPLIT_LINE); System.out.println(begin+"rn"+content+"rn"+end); } public static void print(Object obj){ print(obj,MY_SIGN,objToStr(obj)); } public static void printWithSign(String sign, Object obj) { print(obj, sign,objToStr(obj)); } }

不过呢上面代码太繁琐了，没有考虑多种类型嵌套的问题。

数组类型强转会报ClassCastException 。

平常打日志就用log4j写个工具方法 比上面这个清晰明了多了。

public static void debug(String message,Object o){ int count=0; if(o==null){ LOGGER.debug(chain(message,": null")); return; } if(o.getClass().isArray()){ for(int i=0,len=Array.getLength(o);i<len;i++){ debug(chain(message,"-[",i,"]"),Array.get(o, i)); } }else if(o instanceof Map){ Entry<?,?> e; for(Iterator<?> it=((Map<?,?>)o).entrySet().iterator();it.hasNext();){ e=(Entry<?,?>) it.next(); debug(chain(message,"-[K:",e.getKey(),"]"),e.getValue()); } }else if(o instanceof Iterable){ for(Iterator<?> it=((Iterable<?>) o).iterator();it.hasNext();){ count++; debug(chain(message,"-[",count,"]"),it.next()); } }else{ LOGGER.debug(chain(message,":",o)); } }