Rules for Using Custom GaussDB(DWS) External Functions (pgSQL/Java)

[Notice] Java UDFs can perform some Java logic calculation. Do not encapsulate services in Java UDFs.
[Notice] Do not connect to a database in any way (for example, by using JDBC) in Java functions.
[Notice] Only the data types listed in the following table can be used. User-defined types and complex data types (Java Array and derived classes) are not supported.
[Notice] User-defined aggregation functions (UDAFs) and user-defined table-generating functions (UDTFs) are not supported.

**Table 1** PL/Java mapping for default data types
GaussDB(DWS)	Java
BOOLEAN	boolean
"char"	byte
bytea	byte[]
SMALLINT	short
INTEGER	int
BIGINT	long
FLOAT4	float
FLOAT8	double
CHAR	java.lang.String
VARCHAR	java.lang.String
TEXT	java.lang.String
name	java.lang.String
DATE	java.sql.Timestamp
TIME	java.sql.Time (stored value treated as local time)
TIMETZ	java.sql.Time
TIMESTAMP	java.sql.Timestamp
TIMESTAMPTZ	java.sql.Timestamp