HibernateException: IOException occurred reading text + java.io.IOException: 违反协议: [14,0]

环境：

Hibernate 4.2.7.SP1

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0  64bit production

OJDBC7:12.1.0.1

报错：

数据：向数据库中插入一条数据，数据中某一个字段是CLOB类型，长度为4193个字符

报错异常：

2020-05-20 11:47:23,950 [qtp1288052401-61] c.p.p.m.d.ModelDao ERROR IOException occurred reading text
org.hibernate.HibernateException: IOException occurred reading text
	at org.hibernate.type.descriptor.java.DataHelper.extractString(DataHelper.java:94) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.descriptor.java.DataHelper.extractString(DataHelper.java:280) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.descriptor.java.StringTypeDescriptor.wrap(StringTypeDescriptor.java:89) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.descriptor.java.StringTypeDescriptor.wrap(StringTypeDescriptor.java:39) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.descriptor.sql.ClobTypeDescriptor$1.doExtract(ClobTypeDescriptor.java:60) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.descriptor.sql.BasicExtractor.extract(BasicExtractor.java:64) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:261) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:257) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:247) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.type.AbstractStandardBasicType.hydrate(AbstractStandardBasicType.java:332) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.persister.entity.AbstractEntityPersister.hydrate(AbstractEntityPersister.java:2926) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.loader.Loader.loadFromResultSet(Loader.java:1673) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:1605) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.loader.Loader.getRow(Loader.java:1505) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:713

Caused by: java.io.IOException: 违反协议: [ 14, 0, ]
	at oracle.jdbc.driver.OracleClobReader.needChars(OracleClobReader.java:264) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at oracle.jdbc.driver.OracleClobReader.read(OracleClobReader.java:195) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at org.hibernate.type.descriptor.java.DataHelper.extractString(DataHelper.java:86) ~[hibernate-core-4.2.7.SP1.jar:4.2.7.SP1]
	... 119 more
Caused by: java.sql.SQLException: 违反协议: [ 14, 0, ]
	at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:669) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:249) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at oracle.jdbc.driver.T4C8TTIClob.read(T4C8TTIClob.java:245) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at oracle.jdbc.driver.T4CConnection.getChars(T4CConnection.java:3901) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at oracle.sql.CLOB.getChars(CLOB.java:517) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]
	at oracle.jdbc.driver.OracleClobReader.needChars(OracleClobReader.java:245) ~[ojdbc7-12.1.0.1.jar:12.1.0.1.0]

源码分析：

public static String extractString(Reader reader, int lengthHint) {
		// read the Reader contents into a buffer and return the complete string
		final int bufferSize = getSuggestedBufferSize( lengthHint );
		final StringBuilder stringBuilder = new StringBuilder( bufferSize );
		try {
			char[] buffer = new char[bufferSize];
			while (true) {
				int amountRead = reader.read( buffer, 0, bufferSize );
				if ( amountRead == -1 ) {
					break;
				}
				stringBuilder.append( buffer, 0, amountRead );
			}
		}
		catch ( IOException ioe ) {
			throw new HibernateException( "IOException occurred reading text", ioe );
		}
		finally {
			try {
				reader.close();
			}
			catch (IOException e) {
				LOG.unableToCloseStream( e );
			}
		}
		return stringBuilder.toString();
	}

调试追踪到Hibernate在读取CLOB字段转换为String数据类型时，在read方法处抛出异常：int amountRead = reader.read( buffer, 0, bufferSize );

继续往里追踪，发现，read方法调用的是ojdbc7驱动中的OracleClobReader.read(char[] var1, int var2, int var3)方法:

public int read(char[] var1, int var2, int var3) throws IOException {
        this.ensureOpen();
        int var5 = var2 + Math.min(var3, var1.length - var2);
        if (!this.needChars(var5 - var2)) {
            return -1;
        } else {
            int var4;
            for(var4 = var2 + this.writeChars(var1, var2, var5 - var2); var4 < var5 && this.needChars(var5 - var4); var4 += this.writeChars(var1, var4, var5 - var4)) {
            }
 
            return var4 - var2;
        }
    }

继续追踪，发现是在调用 needChars(int var1) 方法时抛出异常：

protected boolean needChars(int var1) throws IOException {
        this.ensureOpen();
        if (this.pos >= this.count) {
            if (!this.endOfStream) {
                try {
                    if (var1 > this.currentBufferSize) {
                        this.currentBufferSize = Math.max(var1, this.initialBufferSize);
                        PhysicalConnection var2 = (PhysicalConnection)this.clob.getInternalConnection();
                        synchronized(var2) {
                            this.resizableBuffer = var2.getCharBuffer(this.currentBufferSize);
                        }
                    }
 
                    int var7 = this.currentBufferSize;
                    if (this.maxPosition - this.lobOffset < (long)this.currentBufferSize) {
                        var7 = (int)(this.maxPosition - this.lobOffset);
                    }
 
                    this.count = this.clob.getChars(this.lobOffset, var7, this.resizableBuffer);
                    if (this.count < this.currentBufferSize) {
                        this.endOfStream = true;
                    }
 
                    if (this.count > 0) {
                        this.pos = 0;
                        this.lobOffset += (long)this.count;
                        if (this.lobOffset >= this.maxPosition) {
                            this.endOfStream = true;
                        }
 
                        return true;
                    }
                } catch (SQLException var6) {
                    IOException var3 = DatabaseError.createIOException(var6);
                    var3.fillInStackTrace();
                    throw var3;
                }
            }
 
            return false;
        } else {
            return true;
        }
    }

经过对逻辑分析与调试，发现4193长度的字符串调用getInternalConnection会抛出异常，但是加大了了字符串长度到8193后，异常不再抛出，于是怀疑是OJDBC7这个版本的bug，升级到OJDBC7：12.1.0.2后，问题得到解决

疑问：

至于12.1.0.1版本字符串长度为4193时，调用getInternalConnection()方法后会抛出异常的原因还未深究，感兴趣的同学可以了解一下源码，看一下具体问题出现的原因。