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

import java.io.Serializable;

public class Topic implements Serializable{
    private static final long serialVersionUID = 1L;
    private Integer id;
    private String topic;
　　 private byte[] messageData;　　　　　　

　　 public byte[] getMessageData(){
　　　　　　return messageData;
　　}
　　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
　　　　　  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！！！！！
　　}
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getTopic() {
        return topic;
    }
    public void setTopic(String topic) {
        this.topic = topic;
    }
    @Override
    public String toString() {
        return "Topic [id=" + id + ", topic=" + topic + "]";
    }
    public Topic(Integer id, String topic) {
        super();
        this.id = id;
        this.topic = topic;
    }
    public Topic() {
        super();
        // TODO Auto-generated constructor stub
    }
}

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;
    }
}

　

public class MessageData {

    private String destinationChannel;
    
    private String messageId;
    
    private Date absTime;

    public String getDestinationChannel() {
        return destinationChannel;
    }

    public void setDestinationChannel(String destinationChannel) {
        this.destinationChannel = destinationChannel;
    }

    public String getMessageId() {
        return messageId;
    }

    public void setMessageId(String messageId) {
        this.messageId = messageId;
    }

    public Date getAbsTime() {
        return absTime;
    }

    public void setAbsTime(Date absTime) {
        this.absTime = absTime;
    }

    @Override
    public String toString() {
        return "MessageData [destinationChannel=" + destinationChannel + ", messageId=" + messageId + ", absTime="
                + absTime + "]";
    }
    
}

　　

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

   

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;


@RunWith(SpringRunner.class)
@SpringBootTest(classes=启动类.class)
public class SerializeTest {
    
    public static final String INSERTSTOREMESSAGE = "storefoward.intoresendmessage";
    public static final String SELECTRESENDMESSAGE = "storefoward.selectresendmessage";
    
    @Test
    public void serializeTest() throws IOException,ParseException,ApplicationNotFoundException,ClassNotFoundException{
    
        ByteArrayOutputStream bos = null;
        ObjectOutputStream oos =null;
        byte[] serializeTranslateMessage =null;
        
        MessageData message = MessageData();
        
        message.setDestinationChannel("ABC");
        message.setmessageId("1433");
        message.setabsTime("2019.04.01 10:57:34");
        
           //以下是将类序列化成二进制数组存入数据库
        try {
            oos = new ObjectOutputStream(bos=new ByteArrayOutputStream());
            oos.writeObject(message);
        }finally {
            serializeTranslateMessage = bos.toByteArray();
            try {
                oos.close();
                bos.close();
            }catch(IOException e) {
                e.printStackTrace();
            }
        }
        
        Map<String,Object> map = new HashMap<>;
        
        map.put("id","1");
        map.put("topic","method1");
        map.put("messageData",serializeTranslateMessage)  //其中messageData在数据库是以CLOB字段存储
        try {
            int result = DBUtil.insert(INSERTSTOREMESSAGE,map);
        }catch(){
            e.printStackTrace();
        }
        
        //以上是序列化Topic类并存入数据库的操作
        
        //以下是从数据库中取出Topic并反序列化
        
        List<Topic>queryTopicList = null ;
        Map<String,Object> map2 = new HashMap<>;
        
        map2.put("id","1");
        map2.put("topic","method1");
        try {
            queryTopicList = DBUtil.selectList(SELECTRESENDMESSAGE,map2);
        }catch(Exception e) {
            e.printStackTrace();
        }
        
        ObjectInputStream ois = null;
        ByteArrayInputStream bas = null;
        for(int j=0;j<queryTopicList.size();j++) {
            Topic tmpMessage=queryTopicList.get(j);
            try{
                ois = new ObjectInputStream(bas=new ByteArrayInputStream(tmpMessage.getMessageData()));
                Topic deserializeMessage=(Topic)ois.readObject();　　　　//将反序列化后的数据实例化为Topic类
            }catch(IOException e) {
                e.printStackTrace();
                try {
                    ois.close();
                    bas.close();
                }
                catch(IOException E) {
                    E.printStackTrace();
                }
            }
            
        }
    
    }
}

3.mybatis中语句为

<select id = "selectresendmessage" resultType="路径.Topic" parameterType = "java.util.Map">
    SELECT 
        ID,
        TOPIC,
        MESSAGEDATA
    FROM 
        STORE_MESSAGE
    WHERE
      ID = #{id}
    AND
      TOPIC = #{topic}
</select>

<insert id = "intoresendmessage">
    INSERT
    INTO  STORE_MESSAGE
    VALUES(#{id},#{topic},#{messageData}
            )
</insert>