序列化存取数据库（spring+mybatis+oracle） 以及可能会遇到的数据库取出的数据反序列化失败问题

1.需要序列化的类需要实现Serializable方法

例如下面需要序列化的类

 1 import java.io.Serializable;
 2 
 3 public class Topic implements Serializable{
 4     private static final long serialVersionUID = 1L;
 5     private Integer id;
 6     private String topic;
 7 　　 private byte[] messageData;　　　　　　
 8 
 9 　　 public byte[] getMessageData(){
10 　　　　　　return messageData;
11 　　}
12 　　public void setMessageData(String messageData){　　　　　　　　　　　//其中messageData是在数据库中以CLOB字段存储的，将类序列化后存入二进制数组
13 　　　　　  this.messageData = HexTool.decode(messageData);  
　　　　　　//将数据库中取出的CLOB数据类型，实则为二进制数组字符串String进行解码（十六进制字符串-->byte[]） 否则mybatis取出来的字符串无法反序列化！！！！！
14 　　}
15     public Integer getId() {
16         return id;
17     }
18     public void setId(Integer id) {
19         this.id = id;
20     }
21     public String getTopic() {
22         return topic;
23     }
24     public void setTopic(String topic) {
25         this.topic = topic;
26     }
27     @Override
28     public String toString() {
29         return "Topic [id=" + id + ", topic=" + topic + "]";
30     }
31     public Topic(Integer id, String topic) {
32         super();
33         this.id = id;
34         this.topic = topic;
35     }
36     public Topic() {
37         super();
38         // TODO Auto-generated constructor stub
39     }
40 }

public class HexTool{

    //解码：十六进制字符串转换为byte[]
    public static byte[] decode(String hexString) {
        if((hexString.length()%2)!=0) {
            throw new IllegalArgumentException("A HexBinary string must have even length");
        }
        
        byte[] result = new byte[hexString.length()/2];
        int j = 0;
        for(int i=0;i<hexString.length();) {
            byte b;
            char c = hexString.charAt(i++);
            char d = hexString.charAt(i++);
            if(c > = '0' && c<='9') {
                b = (byte)((c - '0') << 4);
            }else if(c > = 'A' && c <= 'F') {
                b=(byte)((c-'A'+10)<<4);
            }else if(c >= 'a' && c<='f') {
                b=(byte)((c-'a'+10)<<4);
            }else {
                throw new IllegalArgumentException("Invalid hex digit:" + c);
            }
            result[j++] = b;
        }
        return result;
    }
}

　

 1 public class MessageData {
 2 
 3     private String destinationChannel;
 4     
 5     private String messageId;
 6     
 7     private Date absTime;
 8 
 9     public String getDestinationChannel() {
10         return destinationChannel;
11     }
12 
13     public void setDestinationChannel(String destinationChannel) {
14         this.destinationChannel = destinationChannel;
15     }
16 
17     public String getMessageId() {
18         return messageId;
19     }
20 
21     public void setMessageId(String messageId) {
22         this.messageId = messageId;
23     }
24 
25     public Date getAbsTime() {
26         return absTime;
27     }
28 
29     public void setAbsTime(Date absTime) {
30         this.absTime = absTime;
31     }
32 
33     @Override
34     public String toString() {
35         return "MessageData [destinationChannel=" + destinationChannel + ", messageId=" + messageId + ", absTime="
36                 + absTime + "]";
37     }
38     
39 }

　　

2.将类序列化后写入二进制数组存入数据库，再取出来反序列化

   

 1 import java.io.ByteArrayInputStream;
 2 import java.io.ByteArrayOutputStream;
 3 import java.io.IOException;
 4 import java.io.ObjectInputStream;
 5 import java.io.ObjectOutputStream;
 6 
 7 
 8 @RunWith(SpringRunner.class)
 9 @SpringBootTest(classes=启动类.class)
10 public class SerializeTest {
11     
12     public static final String INSERTSTOREMESSAGE = "storefoward.intoresendmessage";
13     public static final String SELECTRESENDMESSAGE = "storefoward.selectresendmessage";
14     
15     @Test
16     public void serializeTest() throws IOException,ParseException,ApplicationNotFoundException,ClassNotFoundException{
17     
18         ByteArrayOutputStream bos = null;
19         ObjectOutputStream oos =null;
20         byte[] serializeTranslateMessage =null;
21         
22         MessageData message = MessageData();
23         
24         message.setDestinationChannel("ABC");
25         message.setmessageId("1433");
26         message.setabsTime("2019.04.01 10:57:34");
27         
           //以下是将类序列化成二进制数组存入数据库
28         try {
29             oos = new ObjectOutputStream(bos=new ByteArrayOutputStream());
30             oos.writeObject(message);
31         }finally {
32             serializeTranslateMessage = bos.toByteArray();
33             try {
34                 oos.close();
35                 bos.close();
36             }catch(IOException e) {
37                 e.printStackTrace();
38             }
39         }
40         
41         Map<String,Object> map = new HashMap<>;
42         
43         map.put("id","1");
44         map.put("topic","method1");
45         map.put("messageData",serializeTranslateMessage)  //其中messageData在数据库是以CLOB字段存储
46         try {
47             int result = DBUtil.insert(INSERTSTOREMESSAGE,map);
48         }catch(){
49             e.printStackTrace();
50         }
51         
52         //以上是序列化Topic类并存入数据库的操作
53         
54         //以下是从数据库中取出Topic并反序列化
55         
56         List<Topic>queryTopicList = null ;
57         Map<String,Object> map2 = new HashMap<>;
58         
59         map2.put("id","1");
60         map2.put("topic","method1");
61         try {
62             queryTopicList = DBUtil.selectList(SELECTRESENDMESSAGE,map2);
63         }catch(Exception e) {
64             e.printStackTrace();
65         }
66         
67         ObjectInputStream ois = null;
68         ByteArrayInputStream bas = null;
69         for(int j=0;j<queryTopicList.size();j++) {
70             Topic tmpMessage=queryTopicList.get(j);
71             try{
72                 ois = new ObjectInputStream(bas=new ByteArrayInputStream(tmpMessage.getMessageData()));
73                 Topic deserializeMessage=(Topic)ois.readObject();　　　　//将反序列化后的数据实例化为Topic类
74             }catch(IOException e) {
75                 e.printStackTrace();
76                 try {
77                     ois.close();
78                     bas.close();
79                 }
80                 catch(IOException E) {
81                     E.printStackTrace();
82                 }
83             }
84             
85         }
86     
87     }
88 }

3.mybatis中语句为

 1 <select id = "selectresendmessage" resultType="路径.Topic" parameterType = "java.util.Map">
 2     SELECT 
 3         ID,
 4         TOPIC,
 5         MESSAGEDATA
 6     FROM 
 7         STORE_MESSAGE
 8     WHERE
 9       ID = #{id}
10     AND
11       TOPIC = #{topic}
12 </select>
13 
14 <insert id = "intoresendmessage">
15     INSERT
16     INTO  STORE_MESSAGE
17     VALUES(#{id},#{topic},#{messageData}
18             )
19 </insert>