Building a Java application with Apache Maven

Use this procedure to create and build a Java application with Apache Maven.

Procedure

Create a makefile for your application.
For example, consider the following example hello/hello.mak file.
```
POM_FILE := $(word 1,$(wildcard $(foreach d,$(APPL_ROOT),$d/hello/pom.xml)))
SRC_DIRS := $(wildcard $(foreach d,$(APPL_ROOT),$d/hello/src))
MVN_BLD_DIR := $(word 1,$(APPL_ROOT))/hello/gen
include maketpf.rules_maven
```
The maketpf.rules_maven file defines a default set of makefile rules to compile a Maven project with the maketpf utility. This example specifies the minimum required variables and uses GNU make functions to traverse the APPL_ROOT set of directories to search for the files and directories that are specified by the variables:
- POM_FILE: The absolute path of the Maven application POM configuration file. This file must already exist.
- SRC_DIRS: A list of directories to copy source from, ordered from the highest precedence to the lowest. Each directory must already exist.
- MVN_BLD_DIR: A writable location where the maketpf utility can copy the source to and redirect the Maven build output.
In addition, the following optional variables provide the capability to use and maintain a layered Maven repository with the MakeTPF build solution:
- MVN_REPO_DIRS: A list of directories to treat as repository locations when the application tries to resolve dependencies. These directories do not have to exist.
- MVN_REPO_ADD: Specifies whether you want this Maven project to be contributed to the top layer of the repository. If you set this variable to YES, at least one writable location is required for the MVN_REPO_DIRS variable.
Add a Maven POM configuration file and any source files to the appropriate locations under the TPF_ROOT or APPL_ROOT directories as defined in the makefile.
Update the user control file and user load file with a new entry for the application.
1. Edit the control file and add an entry for your application.
  For example, add the following entry for the hello example application:
```
hello;JAR;hello/hello.mak;1;ALL;OBJ;TPF_SBALL;NOLOAD;;;;;;;;;;;;;;;;;;;;;;;;;;
```
2. Edit the load file and add entries for the names of your application and any dependencies the application might have.
  For example, add the following entries for the helloworld.jar example application and all of its dependencies under the hello/gen/lib directory:
```
hello/gen/helloworld.jar;/sys/tpf_pbfiles/apps/hello;644;tpfdfltu;tpfdfltg;BINARY;ALL;TPF_SBALL;LOAD;;;;;
hello/gen/lib/*;/sys/tpf_pbfiles/apps/hello;644;tpfdfltu;tpfdfltg;BINARY;ALL;TPF_SBALL;LOAD;;;;;
```
The control file entry is required to build the Maven application. The load file entries are required to load the application and its dependencies.
Enter the maketpf command to build the application.
For example:
```
maketpf hello
```
Specify additional maketpf configuration options or build targets as needed to help diagnose any build issues.
1. Set the MAKETPF_MSG_LEVEL option to control the amount of information messages that are generated by Maven. For more information about maketpf configuration options, enter man maketpf.cfg on your Linux® on IBM Z® build system.
2. Run the checkenv target to display the build variables and values that are associated with the Maven application. For more information about maketpf targets, enter man maketpf on your Linux on IBM Z build system.

What to do next

The maketpf utility can enhance the build experience across multiple Apache Maven applications by automatically using a POM configuration to reference commonly defined Maven properties. The maketpf.rules_maven_tpf_properties file contains a list of common version properties that are used across the z/TPF system. The maketpf.rules_maven_user_properties file contains any application-specific properties to be reused. Properties that are defined in these files can be freely referenced by any Maven application without additional configuration changes. For example:

Define a common property such as the following example in the maketpf.rules_maven_tpf_properties file:
```
tpf.log4j.version=2.17.1
```

Update all POM configuration files to use the common property variable. For example:

<dependency>
    <groupId>org.apache.logging.log4j<groupId>
    <artifactId>log4j-api</artifactId>
    <version>${tpf.log4j.version}</version>
</dependency>