Hbase delete遇到的常见异常: Exception in thread "main" java.lang.UnsupportedOperationException
hbase 执行批量删除时出现错误:
Exception in thread "main" java.lang.UnsupportedOperationException at java.util.AbstractList.remove(AbstractList.java:161) at org.apache.hadoop.hbase.client.HTable.delete(HTable.java:852)
这种异常其实很常见,remove操作不支持,为什么会出现不支持的情况呢?检查代码时发现传参list 是通过Arrays.asList()创建的,
很明显,问题就是这个地方导致的,Arrays.asList()返回是实际上是Arrays类内部的一个实现ArrayList:
/** * @serial include */ private static class ArrayList<E> extends AbstractList<E> implements RandomAccess, java.io.Serializable { private static final long serialVersionUID = -2764017481108945198L; private final E[] a; ArrayList(E[] array) { if (array==null) throw new NullPointerException(); a = array; } public int size() { return a.length; } public Object[] toArray() { return a.clone(); } public <T> T[] toArray(T[] a) { int size = size(); if (a.length < size) return Arrays.copyOf(this.a, size, (Class<? extends T[]>) a.getClass()); System.arraycopy(this.a, 0, a, 0, size); if (a.length > size) a[size] = null; return a; } public E get(int index) { return a[index]; } public E set(int index, E element) { E oldValue = a[index]; a[index] = element; return oldValue; } public int indexOf(Object o) { if (o==null) { for (int i=0; i<a.length; i++) if (a[i]==null) return i; } else { for (int i=0; i<a.length; i++) if (o.equals(a[i])) return i; } return -1; } public boolean contains(Object o) { return indexOf(o) != -1; } }
Arrays.ArrayList继承至AbstractList,AbstractList本身是不支持删除操作的,Arrays.ArrayList也没有重现remove方法,因此,如果通过Arrays.asList()创建的ArrayList,如果调用了remove方法,则会出现UnsupportedOperationException异常。