java反射原理制作对象打印工具

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;
 
 

   
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";
 
  
  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);
  }
 
  
  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");
    }
  }
 
  
  private static String mapToStr(Map map, boolean recursion) {
    if (map == null)
      return "null";
    if (isSimpleMap(map) || !recursion)
      return simpleMapToStr(map);
    else
      return complexMapToStr(map, true);
  }
 
  
  private static String simpleMapToStr(Map map) {
    Iterator> i = map.entrySet().iterator();
    if (!i.hasNext())
      return "{}";
 
    StringBuilder sb = new StringBuilder();
    sb.append('{');
    for (int t = 1;; t++) {
      Entry 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> i = map.entrySet().iterator();
    if (!i.hasNext())
      return "{}";
    StringBuilder sb = new StringBuilder();
    sb.append("{rn");
    for (int t = 1;; t++) {
      Entry 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");
    }
  }
 
  
  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);
    }
  }
 
  
  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;
    }
  }
 
  
  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> i = map.entrySet().iterator();
    boolean flag = true;
    while (i.hasNext()) {
      Entry e = i.next();
      if (!isSimpleType(e.getValue())) {
 flag = false;
 break;
      }
    }
    return flag;
  }
 
  
 
  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;
  }
 
  
  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 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));
}
}