我需要能够遍历整个对象图并记录所有成员字段的所有内容。
例如：对象A有一个对象B的集合，它有一个对象C的集合，A，B，C上有其他字段，等等。
Apache Commons ToStringBuilder是不够的，因为它不会遍历对象图或输出集合的内容。
是否有人知道另一个会执行此操作的库或者有一个执行此操作的代码段？
答案 0 :(得分：55)
您可以使用org.apache.commons.lang.builder.ReflectionToStringBuilder遍历整个树。诀窍是在ToStringStyle中你需要遍历价值。 ToStringStyle将处理已经处理的值，并且不允许递归。我们走了：
System.out.println(ReflectionToStringBuilder.toString(schema, new RecursiveToStringStyle(5)));
private static class RecursiveToStringStyle extends ToStringStyle {
private static final int INFINITE_DEPTH = -1;
/**
* Setting {@link #maxDepth} to 0 will have the same effect as using original {@link #ToStringStyle}: it will
* print all 1st level values without traversing into them. Setting to 1 will traverse up to 2nd level and so
* on.
*/
private int maxDepth;
private int depth;
public RecursiveToStringStyle() {
this(INFINITE_DEPTH);
}
public RecursiveToStringStyle(int maxDepth) {
setUseShortClassName(true);
setUseIdentityHashCode(false);
this.maxDepth = maxDepth;
}
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Object value) {
if (value.getClass().getName().startsWith("java.lang.")
|| (maxDepth != INFINITE_DEPTH && depth >= maxDepth)) {
buffer.append(value);
}
else {
depth++;
buffer.append(ReflectionToStringBuilder.toString(value, this));
depth--;
}
}
// another helpful method
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Collection<?> coll) {
depth++;
buffer.append(ReflectionToStringBuilder.toString(coll.toArray(), this, true, true));
depth--;
}
}
答案 1 :(得分：8)
这是@dma_k解决方案的修改版本，具有单缓冲区重用，线程安全性，多行缩进以及对象的toString方法的使用（如果已被覆盖）。
示例输出：
ToStringTest.ParentStub {
array = {a,b,c}
map = {key2=null, key1=value1}
child = ToStringTest.Stub {
field1 = 12345
field2 = Hello
superField = abc
}
empty = <null>
superField = abc
}
代码：
class RecursiveToStringStyle extends ToStringStyle {
private static final RecursiveToStringStyle INSTANCE = new RecursiveToStringStyle(13);
public static ToStringStyle getInstance() {
return INSTANCE;
}
public static String toString(Object value) {
final StringBuffer sb = new StringBuffer(512);
INSTANCE.appendDetail(sb, null, value);
return sb.toString();
}
private final int maxDepth;
private final String tabs;
// http://stackoverflow.com/a/16934373/603516
private ThreadLocal<MutableInteger> depth = new ThreadLocal<MutableInteger>() {
@Override
protected MutableInteger initialValue() {
return new MutableInteger(0);
}
};
protected RecursiveToStringStyle(int maxDepth) {
this.maxDepth = maxDepth;
tabs = StringUtils.repeat("\t", maxDepth);
setUseShortClassName(true);
setUseIdentityHashCode(false);
setContentStart(" {");
setFieldSeparator(SystemUtils.LINE_SEPARATOR);
setFieldSeparatorAtStart(true);
setFieldNameValueSeparator(" = ");
setContentEnd("}");
}
private int getDepth() {
return depth.get().get();
}
private void padDepth(StringBuffer buffer) {
buffer.append(tabs, 0, getDepth());
}
private StringBuffer appendTabified(StringBuffer buffer, String value) {
//return buffer.append(String.valueOf(value).replace("\n", "\n" + tabs.substring(0, getDepth())));
Matcher matcher = Pattern.compile("\n").matcher(value);
String replacement = "\n" + tabs.substring(0, getDepth());
while (matcher.find()) {
matcher.appendReplacement(buffer, replacement);
}
matcher.appendTail(buffer);
return buffer;
}
@Override
protected void appendFieldSeparator(StringBuffer buffer) {
buffer.append(getFieldSeparator());
padDepth(buffer);
}
@Override
public void appendStart(StringBuffer buffer, Object object) {
depth.get().increment();
super.appendStart(buffer, object);
}
@Override
public void appendEnd(StringBuffer buffer, Object object) {
super.appendEnd(buffer, object);
buffer.setLength(buffer.length() - getContentEnd().length());
buffer.append(SystemUtils.LINE_SEPARATOR);
depth.get().decrement();
padDepth(buffer);
appendContentEnd(buffer);
}
@Override
protected void removeLastFieldSeparator(StringBuffer buffer) {
int len = buffer.length();
int sepLen = getFieldSeparator().length() + getDepth();
if (len > 0 && sepLen > 0 && len >= sepLen) {
buffer.setLength(len - sepLen);
}
}
private boolean noReflectionNeeded(Object value) {
try {
return value != null &&
(value.getClass().getName().startsWith("java.lang.")
|| value.getClass().getMethod("toString").getDeclaringClass() != Object.class);
} catch (NoSuchMethodException e) {
throw new IllegalStateException(e);
}
}
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Object value) {
if (getDepth() >= maxDepth || noReflectionNeeded(value)) {
appendTabified(buffer, String.valueOf(value));
} else {
new ReflectionToStringBuilder(value, this, buffer, null, false, false).toString();
}
}
// another helpful method, for collections:
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Collection<?> coll) {
buffer.append(ReflectionToStringBuilder.toString(coll.toArray(), this, true, true));
}
static class MutableInteger {
private int value;
MutableInteger(int value) { this.value = value; }
public final int get() { return value; }
public final void increment() { ++value; }
public final void decrement() { --value; }
}
}
答案 2 :(得分：2)
我不知道一个库，但是使用反射api和一些递归很容易：
printMembers(Object instance)
foreach field
if (field is primitive or String) // guess you're interested in the String value
printPrimitive(field)
else if (field is array or collection)
foreach item in field
printmembers(item)
else
printmembers(field) // no primitve, no array, no collection -> object
获取所有字段对Java Reflection API来说不是问题。如果字段是数组或Iterable的实例，只需使用迭代器来获取所有数组/集合处理程序。
使用自定义实现，您可以自由地为特殊对象添加特殊处理程序（例如将String视为基元），以避免日志混乱。
答案 3 :(得分：0)
这是我为个人使用而编写的内容。让我知道它是否有帮助：
public static String arrayToString(final Object obj){
if (obj == null) {
return "<null>";
}
else {
Object array = null;
if (obj instanceof Collection) {
array = ((Collection) obj).toArray();
}
else if (obj.getClass().isArray()) {
array = obj;
}
else {
return notNull(obj);
}
int length = Array.getLength(array);
int lastItem = length - 1;
StringBuffer sb = new StringBuffer("[");
for (int i = 0; i < length; i++) {
sb.append(arrayToString(Array.get(array, i)));
if (i < lastItem) {
sb.append(", ");
}
}
sb.append(']');
return sb.toString();
}
}
答案 4 :(得分：0)
此链接最终成为一个很好的起点。你基本上需要一些递归的东西，但不会在循环引用中丢失（对象A引用了对象B，它引用了对象A;你不想被一遍又一遍地遍历）。
http://www.java2s.com/Code/Java/Class/Constructsprettystringrepresentationofobjectvalue.htm
这也有点帮助
答案 5 :(得分：0)
扩展了列表和地图的上述代码：
代码：
public class MultipleRecursiveToStringStyle extends ToStringStyle {
private static final int INFINITE_DEPTH = -1;
private int maxDepth;
private int depth;
public MultipleRecursiveToStringStyle() {
this(INFINITE_DEPTH);
}
public MultipleRecursiveToStringStyle(int maxDepth) {
setUseShortClassName(true);
setUseIdentityHashCode(false);
this.maxDepth = maxDepth;
}
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Object value) {
if (value.getClass().getName().startsWith("java.lang.")
|| (maxDepth != INFINITE_DEPTH && depth >= maxDepth)) {
buffer.append(value);
} else {
depth++;
buffer.append(ReflectionToStringBuilder.toString(value, this));
depth--;
}
}
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Collection<?> coll) {
Collections.sort((List<Comparable>) coll);
for(Object value: coll){
if (value.getClass().getName().startsWith("java.lang.")
|| (maxDepth != INFINITE_DEPTH && depth >= maxDepth)) {
buffer.append(value);
} else {
depth++;
buffer.append(ReflectionToStringBuilder.toString(value, this));
depth--;
}
}
}
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Map<?, ?> map) {
TreeMap<?,?> sortedMap = new TreeMap<Object, Object>(map);
for(Map.Entry<?,?> kvEntry: sortedMap.entrySet()){
Object value = kvEntry.getKey();
if (value.getClass().getName().startsWith("java.lang.")
|| (maxDepth != INFINITE_DEPTH && depth >= maxDepth)) {
buffer.append(value);
} else {
depth++;
buffer.append(ReflectionToStringBuilder.toString(value, this));
depth--;
}
value = kvEntry.getValue();
if (value.getClass().getName().startsWith("java.lang.")
|| (maxDepth != INFINITE_DEPTH && depth >= maxDepth)) {
buffer.append(value);
} else {
depth++;
buffer.append(ReflectionToStringBuilder.toString(value, this));
depth--;
}
}
}}
答案 6 :(得分：0)
Apache commons-lang 3.10具有新的RecursiveToStringStyle。
ToStringBuilder.reflectionToString(table, new RecursiveToStringStyle());
Outout
Person@7f54[name=Stephen,age=29,smoker=false,job=Job@43cd2[title=Manager]]