Package com.mckoi.database.global
Class ColumnDescription
- java.lang.Object
-
- com.mckoi.database.global.ColumnDescription
-
public class ColumnDescription extends java.lang.Object
This is a description of a column and the data it stores. Specifically it stores the 'type' as defined in the Types class, the 'size' if the column cells may be different lengths (eg, string), the name of the column, whether the column set must contain unique elements, and whether a cell may be added that is null.- Author:
- Tobias Downer
-
-
Constructor Summary
Constructors Constructor Description ColumnDescription(ColumnDescription cd)
ColumnDescription(java.lang.String name, int type, boolean not_null)
ColumnDescription(java.lang.String name, int type, int size, boolean not_null)
The Constructors if the type does require a size.ColumnDescription(java.lang.String name, ColumnDescription cd)
-
Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Class
classType()
Returns the class of Java object for this field.boolean
equals(java.lang.Object ob)
The 'equals' method, used to determine equality between column descriptions.java.lang.String
getName()
Returns the name of the field.int
getScale()
If this is a number, returns the scale of the field.int
getSize()
Returns the size of the given field.int
getSQLType()
Returns a value from java.sql.Type that is the SQL type defined for this column.java.lang.String
getSQLTypeName()
Returns the name (as a string) of the SQL type or null if the type is not understood.int
getType()
Returns an integer representing the type of the field.int
getUniqueGroup()
Returns the unique group that this column is in.boolean
isNotNull()
Determines whether the field can contain a null value or not.boolean
isNumericType()
Returns true if this column is a numeric type.boolean
isQuantifiable()
Returns true if the type of the field is searchable.boolean
isUnique()
Determines whether the field can contain two items that are identical.static ColumnDescription
readFrom(java.io.DataInputStream in)
Reads a ColumnDescription from the given DataInputStream and returns a new instance of it.void
setScale(int scale)
Sets the scale of the numerical values stored.void
setSQLType(int sql_type)
Sets the SQL type for this ColumnDescription object.void
setUnique()
Sets this column to unique.void
setUniqueGroup(int group)
Sets the column to belong to the specified unique group in the table.void
writeTo(java.io.DataOutputStream out)
Writes this ColumnDescription to the given DataOutputStream.
-
-
-
Constructor Detail
-
ColumnDescription
public ColumnDescription(java.lang.String name, int type, int size, boolean not_null)
The Constructors if the type does require a size.
-
ColumnDescription
public ColumnDescription(java.lang.String name, int type, boolean not_null)
-
ColumnDescription
public ColumnDescription(ColumnDescription cd)
-
ColumnDescription
public ColumnDescription(java.lang.String name, ColumnDescription cd)
-
-
Method Detail
-
setUnique
public void setUnique()
Sets this column to unique. NOTE: This can only happen during the setup of the object. Unpredictable results will occur otherwise.
-
setUniqueGroup
public void setUniqueGroup(int group)
Sets the column to belong to the specified unique group in the table. Setting to -1 sets the column to no unique group. NOTE: This can only happen during the setup of the object. Unpredictable results will occur otherwise.
-
setSQLType
public void setSQLType(int sql_type)
Sets the SQL type for this ColumnDescription object. This is only used to emulate SQL types in the database. They are mapped to the simpler internal types as follows:DB_STRING := CHAR, VARCHAR, LONGVARCHAR DB_NUMERIC := TINYINT, SMALLINT, INTEGER, BIGINT, FLOAT, REAL, DOUBLE, NUMERIC, DECIMAL DB_DATE := DATE, TIME, TIMESTAMP DB_BOOLEAN := BIT DB_BLOB := BINARY, VARBINARY, LONGVARBINARY DB_OBJECT := JAVA_OBJECT
-
setScale
public void setScale(int scale)
Sets the scale of the numerical values stored.
-
getName
public java.lang.String getName()
Returns the name of the field. The field type returned should be 'ZIP' or 'Address1'. To resolve to the tables type, we must append an additional 'Company.' or 'Customer.' string to the front.
-
getType
public int getType()
Returns an integer representing the type of the field. The types are outlined in com.mckoi.database.global.Types.
-
isNumericType
public boolean isNumericType()
Returns true if this column is a numeric type.
-
getSQLType
public int getSQLType()
Returns a value from java.sql.Type that is the SQL type defined for this column. It's possible that the column may not have had the SQL type set in which case we map from the internal db type ( DB_??? ) to the most logical sql type.
-
getSQLTypeName
public java.lang.String getSQLTypeName()
Returns the name (as a string) of the SQL type or null if the type is not understood.
-
classType
public java.lang.Class classType()
Returns the class of Java object for this field.
-
getSize
public int getSize()
Returns the size of the given field. This is only applicable to a few of the types, ie VARCHAR.
-
getScale
public int getScale()
If this is a number, returns the scale of the field.
-
isNotNull
public boolean isNotNull()
Determines whether the field can contain a null value or not. Returns true if it is required for the column to contain data.
-
isUnique
public boolean isUnique()
Determines whether the field can contain two items that are identical. Returns true if each element must be unique.
-
getUniqueGroup
public int getUniqueGroup()
Returns the unique group that this column is in. If it does not belong to a unique group then the value -1 is returned.
-
isQuantifiable
public boolean isQuantifiable()
Returns true if the type of the field is searchable. Searchable means that the database driver can quantify it, as in determine if a given object of the same type is greater, equal or less. We can not quantify BLOB types.
-
equals
public boolean equals(java.lang.Object ob)
The 'equals' method, used to determine equality between column descriptions.- Overrides:
equals
in classjava.lang.Object
-
writeTo
public void writeTo(java.io.DataOutputStream out) throws java.io.IOException
Writes this ColumnDescription to the given DataOutputStream. ( Remember to flush output stream )- Throws:
java.io.IOException
-
readFrom
public static ColumnDescription readFrom(java.io.DataInputStream in) throws java.io.IOException
Reads a ColumnDescription from the given DataInputStream and returns a new instance of it.- Throws:
java.io.IOException
-
-