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Administration of Java Objects

Oracle Tips by Burleson Consulting

In Oracle 8i, Java must first be loaded to make use of it; Oracle9i loads the Java VM automatically through the LoadJava utility, which is described next.

Using LoadJava

Using a built-in PL/SQL package named LoadLobs, the LoadJava utility uploads Java files into a BLOB column in the table create$java$lob$table, which the utility creates in the logon schema. Then it uses the SQL CREATE JAVA statement to load the Java files into the RDBMS.

LoadJava also accepts SQLJ input files (.sqlj files). To process them, it invokes the Server SQLJ Translator, which outputs Java sources and serialized objects for SQLJ profiles (.ser files). Then it invokes the Java compiler, which compiles the Java sources into standard binaries. (For more information, refer to the numerous Java references on the documentation Web site.)

Using a client-side JDBC driver, LoadJava can upload individual Java sources and binaries, SQLJ input files, and entire Java archives (JARs). However, it cannot upload individual resources, so you must put them in a JAR. You can enter .java, .class, .jar, and .sqlj files on the command line in any order. The syntax is:

loadjava

[{-h | -help}]
[{-v | -verbose}]
[{-f | -force}]
[{-r | -resolve}]
[{-a | -andresolve}]
[{-S | -schema} schema_name]
[{-d | -definer}]
[{-s | -synonym}]
[{-g | -grant} {username | role_name}[, {username | role_name}]...]
[{-R | -resolver} "resolver_spec"]
[{-e | -encoding} encoding_scheme_name]
[{-t | -thin} | {-o | -oci81}]
[{-u | -user} username/password@host_name:port_number:database_sid]
{filename.java | filename.class | filename.jar | filename.sqlj} ...

where:

resolver_spec. Specifies schemas to be searched (in the order listed) for referenced Java fullnames. Its syntax is:

((match_string schema_name) (match_string schema_name) ...)

where match_string is a Java fullname; the wildcard, an asterisk (*),which matches any name; or a combination, such as home/java/bin/*; and where schema_name is the name of a schema or the wildcard  (which indicates that names matching the pattern need not be resolved). The default resolver_spec follows:

((* definer's_schema) (* public))

The following list presents the LoadJava command-line options:

 Option     

Description

 -h        

Displays a help screen that lists all the command-line options. 

 -v        

Enables verbose mode, in which progress messages are displayed.

 -f  

Forces the loading of Java classes whether or not they have been loaded before. By default, previously loaded classes are rejected. You cannot force the loading of a binary if you previously loaded the source. You must drop the source first.  

-r   

Compiles all uploaded sources, then resolves external references in uploaded Java classes. Otherwise, sources are compiled and classes are resolved at runtime or when the Java virtual machine (JVM) needs the definitions to resolve other classes. If errors occur during name resolution, they are displayed.

-a   

Works like the -r option except that each uploaded source is compiled and resolved separately. This lets you replace a class that might invalidate other classes. 

-S  

Assigns newly created Java library units to the specified schema. Otherwise, the logon schema is used.  

-s 

Creates public synonyms for uploaded classes. To specify this option, you must have the CREATE PUBLIC  SYNONYM privilege.

  -d  

Specifies that the methods of uploaded classes will execute with the privileges of their definer, not their invoker.

 -g   

Grants the EXECUTE privilege on uploaded classes and resources to the listed users and/or roles. (To call the methods of a class directly, users must have the EXECUTE privilege.)

-R   

Specifies a resolver spec, which is bound to newly created Java library units. Because it contains spaces, the resolver spec must be enclosed by double quotation marks. 

 -e  

Sets the encoding option in the database table java$options to the specified value, which must be a standard JDK encoding-scheme name. The encoding of uploaded sources must match the specified encoding.

-t | -o    

Selects the client-side JDBC driver used to communicate with Oracle. You can choose the Thin JDBC Driver (the default) or the OCI JDBC Driver. For information about these drivers, see the JDBC reference on the documentation Web site.

-u   

Specifies a database connect string without spaces. The string includes a user name, password, host-computer name, port number, and database system identifier. If this option is not specified, the string defaults to internal/oracle@localhost:1521:orcl.   

Caution: LoadJava uses the hash table java$class$md5$table to track the loading of Java library units into a schema (md5 refers to RSA Data Security痴 MD5 Message-Digest Algorithm, which does the hashing). If you use LoadJava to load a Java library unit, you must use DropJava to drop the unit. Otherwise, the table will not be updated properly.  Also, if you use the SQL DROP JAVA statement to drop a Java class, and then use LoadJava to upload the same class, you must specify the force (-f) command-line option. Otherwise, the upload fails.

LoadJava Examples  

In the first example, LoadJava uploads archived Java binaries and resources from an OS file system (> is the prompt). The utility reads the JAR files, stores each binary or resource in a database row keyed by the filename of the class or resource, then uses the SQL CREATE JAVA statement to load the Java files into the RDBMS.

> loadjava -u scott/tiger@myComputer:1521:orcl managers.jar
managerText.jar

In the next example, operating in verbose mode, LoadJava uploads and resolves a Java source file. The force (-f) option forces the loading of the file. The resolve option (-r) compiles the file and resolves external references; also, by reporting resolution errors, it helps to identify missing classes.

> loadjava -v -f -r -u scott/tiger@myComputer:1521:orcl Agent.java

Load Lobs package already installed:

loading  : Agent

creating : Agent

resolving: Agent

In the following example, a name resolver is specified:

> loadjava -R "((/home/java/bin/* scott) (* public))"
-u scott/tiger@myComputer:1521:orcl Swapper.class

If the path to a file begins with a slash, LoadJava prefixes the word ROOT to the Java fullname, as the following example shows:

> loadjava -v -f -u scott/tiger@myComputer:1521:orcl
/routines/java/src/Alerter.java

Load Lobs package already installed:

loading  : ROOT/routines/java/src/Alerter
creating : ROOT/routines/java/src/Alerter

Checking Upload Results

To check upload results, you can query the database view user_objects, which contains information about schema objects owned by the user (Scott, in this case). For example, the following SQL*Plus script formats and displays useful information about uploaded Java sources, binaries, and resources:

SET SERVEROUTPUT ON
SET VERIFY OFF
PROMPT A)ll or J)ava only?
ACCEPT x CHAR PROMPT 'Choice: '
DECLARE
  choice CHAR(1) := UPPER('&x');
  printable BOOLEAN;
  bad_choice EXCEPTION;

BEGIN
  IF choice NOT IN ('A', 'J') THEN RAISE bad_choice; END IF;
  DBMS_OUTPUT.PUT_LINE(CHR(0));
  DBMS_OUTPUT.PUT_LINE('Object Name                    ' ||
    'Object Type   Status  Timestamp');
  DBMS_OUTPUT.PUT_LINE('覧覧覧覧覧覧覧 ' ||
    '覧覧覧- 覧- 覧覧覧覧');
  FOR i IN (SELECT object_name, object_type, status, timestamp
    FROM user_objects ORDER BY object_type, object_name)
  LOOP
    /* Exclude objects generated for LoadJava and DropJava. */
    printable := i.object_name NOT LIKE 'SYS_%'
      AND i.object_name NOT LIKE 'CREATE$%'
      AND i.object_name NOT LIKE 'JAVA$%'
      AND i.object_name NOT LIKE 'LOADLOBS';
    IF choice = 'J' THEN
      printable := i.object_type LIKE 'JAVA %';
    END IF;
    IF printable THEN
      DBMS_OUTPUT.PUT_LINE(RPAD(i.object_name,31) ||
        RPAD(i.object_type,14) ||
        RPAD(i.status,8) || SUBSTR(i.timestamp,1,16));
    END IF;
  END LOOP;
EXCEPTION
  WHEN bad_choice THEN
    DBMS_OUTPUT.PUT_LINE('Bad choice');
END;
/

You can choose to display all your schema objects or only the Java objects:

SQL> @usr_obj
A)ll or J)ava only?
Choice: a

Object Name                   Object Type   Status  Timestamp
覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧
Alerter                       JAVA CLASS    VALID   1998-10-08:13:42
POManager                     JAVA CLASS    VALID   1998-10-08:17:14
Alerter                       JAVA Source   VALID   1998-10-08:13:42
POManager                     JAVA Source   VALID   1998-10-08:17:11
BONUS                         TABLE         VALID   1998-10-08:14:02
DEPT                          TABLE         VALID   1998-10-08:14:02
EMP                           TABLE         VALID   1998-10-08:14:02
SALGRADE                      TABLE         VALID   1998-10-08:14:02

SQL> @usr_obj
A)ll or J)ava only?
Choice: j

Object Name                   Object Type   Status  Timestamp
覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧
Alerter                       JAVA CLASS    VALID   1998-10-08:13:42
POManager                     JAVA CLASS    VALID   1998-10-08:17:14
Alerter                       JAVA Source   VALID   1998-10-08:13:42
POManager                     JAVA Source   VALID   1998-10-08:17:11

The column object_name stores Java fullnames. However, if a name is longer than 30 characters or contains an untranslatable character, the shortname is stored instead. To convert shortnames to fullnames, you can use the function longname in the utility package DBMS_JAVA, as follows:

SQL> SELECT dbms_java.longname(object_name), ... FROM user_objects;

Table 7.1 describes all the columns in database view user_objects.

Table 7.1   USER_OBJECTS View Columns

Column Name

Datatype   

Description

OBJECT_NAME     

VARCHAR2(128)    

Name of the object

SUBOBJECT_NAME  

VARCHAR2(30)     

Name of any subobject (a partition, for example)

OBJECT_ID 

NUMBER     

 Object number of the object

 DATA_OBJECT_ID  

NUMBER     

Object number of the segment that contains the object

OBJECT_TYPE

VARCHAR2(15)     

Type of object (a table or index, for example) 

CREATED   

DATE 

 Date on which the object was created

LAST_DDL_TIME

DATE 

Date of the last DDL operation on the object

TIMESTAMP

VARCHAR2(19)

Character string containing the date and time the object was created

STATUS    

VARCHAR2(7)

Status (valid or invalid) of the object

TEMPORARY

VARCHAR2(1)

Indicator (y/n) of whether or not the current session sees only the data that it stores in the object

GENERATED 

VARCHAR2(1)

Indicator of whether or not the name of the object was generated by the system

SECONDARY 

 VARCHAR2(1)

Indicator of whether or not this is a secondary object created for domain indexes


See Code Depot for Full Scripts


This is an excerpt from Mike Ault, bestselling author of "Oracle 10g Grid and Real Application Clusters".

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.

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