Java可序列化的HashMap到ByteArray用于创建Blob

Question

When I tried it, I get this message error:

java.io.NotSerializableException:

  private HashMap<String, XlsData> myMap= new HashMap<String, XlsData>();

        ByteArrayOutputStream bObj = new ByteArrayOutputStream();
            ObjectOutputStream out;
                try {
                out = new ObjectOutputStream(bObj);
                if(myMap != null){
                out.writeObject(myMap);
                out.close();
                bObj.close();
                byte[] byteOut = bObj.toByteArray();
              }
              } catch (IOException e) {
                e.printStackTrace();
            }

    public class XlsData implements Serializable {

            private String dataA;
            private String dataB;

            public String getDataA() {
                return dataA;
            }
            public void setDataA(String dataA) {
                this.dataA= dataA;
            }
            public String getDataB() {
                return dataB;
            }
            public void setDataB(String dataB) {
                this.dataB= dataB;
            }
}

What it's necessary to works fine? As it's possible see my inner class implements a serializabe class too.

Answer 1

Your XlsData class needs to be a static inner class:

public static class XlsData implements Serializable {

Because it is not static, it behaves like a non-static field: it can only exist as part of an instance of the outer class. When you serialize an instance of a non-static inner class, you are also serializing the enclosing outer class object, which I'm guessing is not serializable (or one or more of its fields is not serializable).

Answer 2

Most likely, simply one of the elements of you're map isn't serializable. Or an element of the map holds a member that is neither serializable nor transient. Just look through the map and you should find the answer.