ValueLob (H2 Database Engine wt-1.0.1 API)

java.lang.Object
- org.h2.value.Value
- - org.h2.value.ValueLob

```
public class ValueLob
extends Value
```
Implementation of the BLOB and CLOB data types. Small objects are kept in memory and stored in the record. Large objects are stored in their own files. When large objects are set in a prepared statement, they are first stored as 'temporary' files. Later, when they are used in a record, and when the record is stored, the lob files are linked: the file is renamed using the file format (tableId).(objectId). There is one exception: large variables are stored in the file (-1).(objectId). When lobs are deleted, they are first renamed to a temp file, and if the delete operation is committed the file is deleted. Data compression is supported.

嵌套类概要
- 从类继承的嵌套类/接口 org.h2.value.Value
  Value.ValueBlob, Value.ValueClob

字段概要
- 从类继承的字段 org.h2.value.Value
  ARRAY, BLOB, BOOLEAN, BYTE, BYTES, CLOB, DATE, DECIMAL, DOUBLE, FLOAT, GEOMETRY, INT, JAVA_OBJECT, LONG, NULL, RESULT_SET, SHORT, STRING, STRING_FIXED, STRING_IGNORECASE, TIME, TIMESTAMP, TIMESTAMP_TZ, TYPE_COUNT, UNKNOWN, UUID

方法概要

所有方法静态方法实例方法具体方法
限定符和类型	方法和说明
`protected int`	`compareSecure(Value v, CompareMode mode)` Compare the value with another value of the same type.
`Value`	`convertPrecision(long precision, boolean force)` Convert the precision to the requested value.
`Value`	`convertTo(int t)` Convert a lob to another data type.
`void`	`convertToFileIfRequired(DataHandler h)` Store the lob data to a file if the size of the buffer is larger than the maximum size for an in-place lob.
`Value`	`copy(DataHandler h, int tabId)` Copy a large value, to be used in the given table.
`ValueLob`	`copyToTemp()` Create an independent copy of this temporary value.
`boolean`	`equals(Object other)` Check if the two values have the same hash code.
`byte[]`	`getBytes()`
`byte[]`	`getBytesNoCopy()`
`int`	`getDisplaySize()` Get the display size in characters.
`String`	`getFileName()` Get the current file name where the lob is saved.
`InputStream`	`getInputStream()`
`int`	`getMemory()` Get the memory used by this object.
`Object`	`getObject()` Get the value as an object.
`int`	`getObjectId()` Get the current object id of this lob.
`long`	`getPrecision()` Get the precision.
`Reader`	`getReader()`
`byte[]`	`getSmall()` Get the data if this a small lob value.
`String`	`getSQL()` Get the SQL expression for this value.
`String`	`getString()` Get the value as a string.
`int`	`getTableId()` Get the current table id of this lob.
`String`	`getTraceSQL()` Get a medium size SQL expression for debugging or tracing.
`int`	`getType()` Get the value type.
`int`	`hashCode()`
`boolean`	`isCompressed()` Check if this lob value is compressed.
`boolean`	`isLinkedToTable()` Check if this value is linked to a specific table.
`static ValueLob`	`openLinked(int type, DataHandler handler, int tableId, int objectId, long precision, boolean compression)` Create a LOB value with the given parameters.
`static ValueLob`	`openUnlinked(int type, DataHandler handler, int tableId, int objectId, long precision, boolean compression, String fileName)` Create a LOB value with the given parameters.
`void`	`remove()` Remove the underlying resource, if any.
`void`	`set(PreparedStatement prep, int parameterIndex)` Set the value as a parameter in a prepared statement.

从类继承的方法 org.h2.value.Value
add, checkPrecision, clearCache, compareTo, compareTypeSafe, convertScale, copyToResult, divide, getBigDecimal, getBoolean, getByte, getDataHandler, getDate, getDouble, getFloat, getHigherOrder, getInt, getLong, getResultSet, getScale, getShort, getSignum, getTime, getTimestamp, modulus, multiply, negate, subtract, throwUnsupportedExceptionForType, toString

从类继承的方法 java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- 方法详细资料
  - openLinked
```
public static ValueLob openLinked(int type,
                                  DataHandler handler,
                                  int tableId,
                                  int objectId,
                                  long precision,
                                  boolean compression)
```
    Create a LOB value with the given parameters.
    
    参数:
    
    type - the data type
    
    handler - the file handler
    
    tableId - the table object id
    
    objectId - the object id
    
    precision - the precision (length in elements)
    
    compression - if compression is used
    
    返回:
    
    the value object
  - openUnlinked
```
public static ValueLob openUnlinked(int type,
                                    DataHandler handler,
                                    int tableId,
                                    int objectId,
                                    long precision,
                                    boolean compression,
                                    String fileName)
```
    Create a LOB value with the given parameters.
    
    参数:
    
    type - the data type
    
    handler - the file handler
    
    tableId - the table object id
    
    objectId - the object id
    
    precision - the precision (length in elements)
    
    compression - if compression is used
    
    fileName - the file name
    
    返回:
    
    the value object
  - convertTo
```
public Value convertTo(int t)
```
    Convert a lob to another data type. The data is fully read in memory except when converting to BLOB or CLOB.
    
    覆盖:
    
    convertTo 在类中 Value
    
    参数:
    
    t - the new type
    
    返回:
    
    the converted value
  - isLinkedToTable
```
public boolean isLinkedToTable()
```
    从类复制的说明: Value
    
    Check if this value is linked to a specific table. For values that are kept fully in memory, this method returns false.
    
    覆盖:
    
    isLinkedToTable 在类中 Value
    
    返回:
    
    true if it is
  - getFileName
```
public String getFileName()
```
    Get the current file name where the lob is saved.
    
    返回:
    
    the file name or null
  - remove
```
public void remove()
```
    从类复制的说明: Value
    
    Remove the underlying resource, if any. For values that are kept fully in memory this method has no effect.
    
    覆盖:
    
    remove 在类中 Value
  - copy
```
public Value copy(DataHandler h,
                  int tabId)
```
    从类复制的说明: Value
    
    Copy a large value, to be used in the given table. For values that are kept fully in memory this method has no effect.
    
    覆盖:
    
    copy 在类中 Value
    
    参数:
    
    h - the data handler
    
    tabId - the table where this object is used
    
    返回:
    
    the new value or itself
  - getTableId
```
public int getTableId()
```
    Get the current table id of this lob.
    
    覆盖:
    
    getTableId 在类中 Value
    
    返回:
    
    the table id
  - getObjectId
```
public int getObjectId()
```
    Get the current object id of this lob.
    
    返回:
    
    the object id
  - getType
```
public int getType()
```
    从类复制的说明: Value
    
    Get the value type.
    
    指定者:
    
    getType 在类中 Value
    
    返回:
    
    the type
  - getPrecision
```
public long getPrecision()
```
    从类复制的说明: Value
    
    Get the precision.
    
    指定者:
    
    getPrecision 在类中 Value
    
    返回:
    
    the precision
  - getString
```
public String getString()
```
    从类复制的说明: Value
    
    Get the value as a string.
    
    指定者:
    
    getString 在类中 Value
    
    返回:
    
    the string
  - getBytes
```
public byte[] getBytes()
```
    覆盖:
    
    getBytes 在类中 Value
  - getBytesNoCopy
```
public byte[] getBytesNoCopy()
```
    覆盖:
    
    getBytesNoCopy 在类中 Value
  - hashCode
```
public int hashCode()
```
    指定者:
    
    hashCode 在类中 Value
  - compareSecure
```
protected int compareSecure(Value v,
                            CompareMode mode)
```
    从类复制的说明: Value
    
    Compare the value with another value of the same type.
    
    指定者:
    
    compareSecure 在类中 Value
    
    参数:
    
    v - the other value
    
    mode - the compare mode
    
    返回:
    
    0 if both values are equal, -1 if the other value is smaller, and 1 otherwise
  - getObject
```
public Object getObject()
```
    从类复制的说明: Value
    
    Get the value as an object.
    
    指定者:
    
    getObject 在类中 Value
    
    返回:
    
    the object
  - getReader
```
public Reader getReader()
```
    覆盖:
    
    getReader 在类中 Value
  - getInputStream
```
public InputStream getInputStream()
```
    覆盖:
    
    getInputStream 在类中 Value
  - set
```
public void set(PreparedStatement prep,
                int parameterIndex)
         throws SQLException
```
    从类复制的说明: Value
    
    Set the value as a parameter in a prepared statement.
    
    指定者:
    
    set 在类中 Value
    
    参数:
    
    prep - the prepared statement
    
    parameterIndex - the parameter index
    
    抛出:
    
    SQLException
  - getSQL
```
public String getSQL()
```
    从类复制的说明: Value
    
    Get the SQL expression for this value.
    
    指定者:
    
    getSQL 在类中 Value
    
    返回:
    
    the SQL expression
  - getTraceSQL
```
public String getTraceSQL()
```
    从类复制的说明: Value
    
    Get a medium size SQL expression for debugging or tracing. If the precision is too large, only a subset of the value is returned.
    
    覆盖:
    
    getTraceSQL 在类中 Value
    
    返回:
    
    the SQL expression
  - getSmall
```
public byte[] getSmall()
```
    Get the data if this a small lob value.
    
    覆盖:
    
    getSmall 在类中 Value
    
    返回:
    
    the data
  - getDisplaySize
```
public int getDisplaySize()
```
    从类复制的说明: Value
    
    Get the display size in characters.
    
    指定者:
    
    getDisplaySize 在类中 Value
    
    返回:
    
    the display size
  - equals
```
public boolean equals(Object other)
```
    从类复制的说明: Value
    
    Check if the two values have the same hash code. No data conversion is made; this method returns false if the other object is not of the same class. For some values, compareTo may return 0 even if equals return false. Example: ValueDecimal 0.0 and 0.00.
    
    指定者:
    
    equals 在类中 Value
    
    参数:
    
    other - the other value
    
    返回:
    
    true if they are equal
  - convertToFileIfRequired
```
public void convertToFileIfRequired(DataHandler h)
```
    Store the lob data to a file if the size of the buffer is larger than the maximum size for an in-place lob.
    
    参数:
    
    h - the data handler
  - isCompressed
```
public boolean isCompressed()
```
    Check if this lob value is compressed.
    
    返回:
    
    true if it is
  - getMemory
```
public int getMemory()
```
    从类复制的说明: Value
    
    Get the memory used by this object.
    
    覆盖:
    
    getMemory 在类中 Value
    
    返回:
    
    the memory used in bytes
  - copyToTemp
```
public ValueLob copyToTemp()
```
    Create an independent copy of this temporary value. The file will not be deleted automatically.
    
    覆盖:
    
    copyToTemp 在类中 Value
    
    返回:
    
    the value
  - convertPrecision
```
public Value convertPrecision(long precision,
                              boolean force)
```
    从类复制的说明: Value
    
    Convert the precision to the requested value. The precision of the returned value may be somewhat larger than requested, because values with a fixed precision are not truncated.
    
    覆盖:
    
    convertPrecision 在类中 Value
    
    参数:
    
    precision - the new precision
    
    force - true if losing numeric precision is allowed
    
    返回:
    
    the new value

类 ValueLob

嵌套类概要

从类继承的嵌套类/接口 org.h2.value.Value

字段概要

从类继承的字段 org.h2.value.Value

方法概要

从类继承的方法 org.h2.value.Value

从类继承的方法 java.lang.Object

方法详细资料

openLinked

openUnlinked

convertTo

isLinkedToTable

getFileName

remove

copy

getTableId

getObjectId

getType

getPrecision

getString

getBytes

getBytesNoCopy

hashCode

compareSecure

getObject

getReader

getInputStream

set

getSQL

getTraceSQL

getSmall

getDisplaySize

equals

convertToFileIfRequired

isCompressed

getMemory

copyToTemp

convertPrecision