Save and restore existing system properties in maven plugin

[markcuk]

Currently the maven plugin sets system properties when environmentVariables are specified in the pom. These system properties are never reset however and therefore in a multi-module maven build or in an IDE such as Eclipse those system properties will interfere with other modules that are also using the swagger-codegen maven plugin.

For example if I have module a that generates model objects and module b that generates apis if I run a multi-module build (with a running then b) module b will generate both model objects and apis.

[ePaul]

I just did hit this too (two executions of the plugin, where only one was setting the models property, but both got the setting).

           <plugin>
              <groupId>io.swagger</groupId>
              <artifactId>swagger-codegen-maven-plugin</artifactId>
              <version>2.1.6</version>
              <executions>
                  <execution>
                      <id>nakadi-api</id>
                      <goals>
                          <goal>generate</goal>
                      </goals>
                      <configuration>
                          <inputSpec>src/main/resources/api/nakadi-event-bus-api.yaml</inputSpec>
                          <language>springinterfacesNoSwaggerAnnotations</language>
                          <configOptions>
                            <modelPackage>org.zalando.tarbela.nakadi.models</modelPackage>
                            <apiPackage>org.zalando.tarbela.nakadi.api</apiPackage>
                            <invokerPackage>org.zalando.tarbela.nakadi</invokerPackage>
                            <configOptions>
                                <import-mappings>Data=java.util.HashMap&lt;String,Object&gt;</import-mappings>
                            </configOptions>
                            <sourceFolder></sourceFolder>
                          </configOptions>
                          <environmentVariables>
                              <models></models>
                          </environmentVariables>
                      </configuration>
                  </execution>
                  <execution>
                      <id>producer-api</id>
                      <goals>
                          <goal>generate</goal>
                      </goals>
                      <configuration>
                          <inputSpec>src/main/resources/api/event-producer-api.yaml</inputSpec>
                          <language>springinterfacesNoSwaggerAnnotations</language>
                          <configOptions>
                            <modelPackage>org.zalando.tarbela.producer.models</modelPackage>
                            <apiPackage>org.zalando.tarbela.producer.api</apiPackage>
                            <invokerPackage>org.zalando.tarbela.producer</invokerPackage>
                            <skipApigeneration>true</skipApigeneration>
                            <sourceFolder></sourceFolder>
                          </configOptions>
                      </configuration>
                  </execution>
              </executions>
                <dependencies>
                    <dependency>
                        <groupId>org.zalando.stups</groupId>
                        <artifactId>swagger-codegen-template-spring-interfaces</artifactId>
                        <version>${zalando-swagger-codegen-plugin-version}</version>
                    </dependency>
                </dependencies>
           </plugin>
        </plugins>

It looks like the setting of system properties was added in #1428. I think it is basically a bad idea to use System properties for transferring information inside one module – these are like global variables, but worse, as they leak to other modules which might using the same name for other goals, or, as in my case, a different instance of the same module which should not get it.

For setting information from the outside (e.g. the command line) system properties are acceptable, it is then the responsibility of the setter to make sure they don't leak. Inside they should not be set.