If all references are resolved, then the resolver marks the class valid. Ensure that you correctly load the resource files that your classes require.įor each interclass reference in a class, the resolver searches the schemas specified by the resolver specification for a valid class schema object that satisfies the reference. Also, run-time resolution can fail for lack of database resources, if the tree of classes is very large.Īs with the Java compiler, the loadjava tool resolves references to classes, but not to resources. Unsuccessful resolution at run time produces a ClassNotFound exception. If the class that you load contains a reference to a class that is not found within the appropriate schemas, then the class is listed as invalid. When locating and resolving the interclass dependencies for classes, the resolver marks each class as valid or invalid, depending on whether all interdependent classes are located. This is in contrast to a classic JVM, where CLASSPATH is global to all classes. Resolver specifications are defined for each class. ![]() The listing of schemas to search is known as a resolver specification. For example, if your schema is HR, then the database resolver searches the HR schema before searching the PUBLIC schema. ![]() If your classes depend on other classes you have defined, then you will probably load them all within your own schema. All predefined Java application programming interfaces (APIs), such as java.lang.*, are loaded within the PUBLIC schema. In Oracle Database, because you load all Java classes into the database, you may need to specify where to find the dependent classes for your Java class within the database.Īll classes loaded within the database are referred to as class schema objects and are loaded within certain schemas. In contrast, Oracle JVM searches database schemas for class objects. jar files within the directories specified in CLASSPATH. Many Java classes contain references to other classes, which is the essence of reusing code. The loadjava tool also provides the facilities for forcing compilation and resolution if you do not want the dependency management facilities to perform this for you. You must force compilation and resolution yourself only if you are developing and you want to find problems early. The dependency system enables you to rely on Oracle Database to manage dependencies between classes, to recompile, and to resolve automatically. Note that classes can be recompiled only if the source file is present on the server. Before you use any of these classes again, Oracle Database attempts to resolve them and recompile, if necessary. If you change the definition of class A by adding a new field to it, then the dependency mechanism in Oracle Database flags classes B and C as invalid. In the preceding example, you can see that classes A, B, and C depend on one another, because A holds an instance of B, B holds an instance of C, and C holds an instance of A. The system tracks dependencies at a class level of granularity. Consider the following example: public class A Oracle Database provides a dependency management and automatic build facility that transparently recompiles source programs when you make changes to the source or binary programs upon which they depend. The packages and classes are compiled with online=false.Īll other packages and classes match the empty string entry and are compiled with online=true. The name a.b matches class and package names beginning with a.b. The packages and classes are compiled with online=true. The name a.b.c.d matches class and package names beginning with a.b.c.d. The online option shown in the table matches schema object names as follows: Because the table has no entry for the encoding option, the compiler uses the default or the value specified on the command line. The schema name with a higher resolution for the pattern match is the entry that applies. ![]() The pattern match rule is to match as much of the schema name against the table entry as possible. The following table represents a hypothetical JAVA$OPTIONS database table. ![]() SQL> execute dbms_t_compiler_option('x.y', 'online', 'false') The procedure will create the table, if it does not exist. To create a JAVA$OPTIONS table, use the t_compiler_option procedure from the DBMS_JAVA package to set a value. Initially, a schema does not have a JAVA$OPTIONS table.
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