+++
title = "Java Proto Names"
weight = 655
linkTitle = "Generated Proto Names"
description = "Names that are generated by the Java protoc plugin."
type = "docs"
+++

This document contains information on what the fully-qualified Java name of a
proto is, based on the different proto options. This name corresponds to the
package you need to import to use that message.

## Recommendation { #recommendation }

*   Set `option java_multiple_files = true;`
*   Set `option java_outer_classname = "FileNameProto";`
*   Set `option java_package = "com.google.package";`

### Explanation {#explanation}

#### Multiple Files {#multiple-files}

With `java_multiple_files = true`, the generated Java class for each message
will be placed in a separate `.java` file. This makes it much easier to move
messages from one `.proto` file to another.

#### Outer Classname {#outer-classname}

There is a Java class generated for the `.proto` file itself. The name of the
class for the file will be automatically generated if not specified. However,
the rules for how that name is generated are overly-complicated and non-obvious.
The best policy is to explicitly set the `java_outer_classname` option to the
`.proto` file name converted to PascalCase with the `'.'` removed. For example:

*   The file `student_record_request.proto` should set:

    ```proto
    option java_outer_classname = "StudentRecordRequestProto";
    ```

#### Java Package {#java-package}

The Java package for generated bindings will be automatically set to the proto
package. However, this is usually not conformant with Java conventions. To
ensure a conventional Java package name, we recommend explicitly setting the
`java_package` option. For example, within Google, the convention is to prepend
`com.google.` to the proto package.

## Immutable API Message Names { #immutable-api-message-names }

The Java plugin for protoc will generate names according to this table.

java_multiple_files | java_package | java_outer_classname | Generated full message name
:-----------------: | ------------ | -------------------- | ---------------------------
true                | Not defined  | *ignored*            | `com.google.protos.$package.$message`
true                | Defined      | *ignored*            | `$java_package.$message`
false               | Not defined  | Not defined          | `com.google.protos.$package.$derived_outer_class.$message`
false               | Not defined  | Defined              | `com.google.protos.$package.$java_outer_classname.$message`
false               | Defined      | Not defined          | `$java_package.$derived_outer_class.$message`
false               | Defined      | Defined              | `$java_package.$java_outer_classname.$message`

**Legend**

*   `$message` is the actual name of the proto message.
*   `$package` is the name of the proto package. This is the name specified by
    the `package` directive in the proto file, which is usually at the top of
    the file.
*   `$derived_outer_class` is a name generated from the proto file name.
    Generally it's computed by removing punctuation from the file name and
    converting it to PascalCase. For example, if the proto is `foo_bar.proto`,
    the `$derived_outer_class` value is `FooBar`.

    If the generated class name would be the same as one of the messages defined
    in the proto file, `derived_outer_class` has `OuterClass` appended to it.
    For example, if the proto is `foo_bar.proto` and contains a `FooBar`
    message, the `$derived_outer_class` value is `FooBarOuterClass`. The same is
    true when using the v1 API, whether or not the class name would be the same
    as one of the messages defined.

*   All other `$names` are the values of the corresponding file options defined
    in the `.proto` file.