Add file post-processing support for Java generators (#1052)

* add clang format support for java

* rename java env variable

* fix export command

Author: wing328

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java

@@ -27,6 +27,7 @@
 import io.swagger.v3.oas.models.media.StringSchema;
 import io.swagger.v3.parser.util.SchemaTypeUtil;
 
+import org.apache.commons.io.FilenameUtils;
 import org.apache.commons.lang3.BooleanUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.CliOption;
@@ -212,6 +213,10 @@ public AbstractJavaCodegen() {
     public void processOpts() {
         super.processOpts();
 
+        if (StringUtils.isEmpty(System.getenv("JAVA_POST_PROCESS_FILE"))) {
+            LOGGER.info("Environment variable JAVA_POST_PROCESS_FILE not defined so the Java code may not be properly formatted. To define it, try 'export JAVA_POST_PROCESS_FILE=\"/usr/local/bin/clang-format -i\"' (Linux/Mac)");
+        }
+
         if (additionalProperties.containsKey(SUPPORT_JAVA6)) {
             this.setSupportJava6(Boolean.valueOf(additionalProperties.get(SUPPORT_JAVA6).toString()));
         }
@@ -226,7 +231,6 @@ public void processOpts() {
             this.setBooleanGetterPrefix(additionalProperties.get(BOOLEAN_GETTER_PREFIX).toString());
         }
         additionalProperties.put(BOOLEAN_GETTER_PREFIX, booleanGetterPrefix);
-
         if (additionalProperties.containsKey(USE_NULL_FOR_UNKNOWN_ENUM_VALUE)) {
             this.setUseNullForUnknownEnumValue(Boolean.valueOf(additionalProperties.get(USE_NULL_FOR_UNKNOWN_ENUM_VALUE).toString()));
         }
@@ -1382,6 +1386,35 @@ public String sanitizeTag(String tag) {
         return tag;
     }
 
+    @Override
+    public void postProcessFile(File file, String fileType) {
+        if (file == null) {
+            return;
+        }
+
+        String javaPostProcessFile = System.getenv("JAVA_POST_PROCESS_FILE");
+        if (StringUtils.isEmpty(javaPostProcessFile)) {
+            return; // skip if JAVA_POST_PROCESS_FILE env variable is not defined
+        }
+
+        // only process files with hs extension
+        if ("java".equals(FilenameUtils.getExtension(file.toString()))) {
+            String command = javaPostProcessFile + " " + file.toString();
+            try {
+                Process p = Runtime.getRuntime().exec(command);
+                p.waitFor();
+                int exitValue = p.exitValue();
+                if (exitValue != 0) {
+                    LOGGER.error("Error running the command ({}). Exit value: {}", command, exitValue);
+                } else {
+                    LOGGER.info("Successfully executed: " + command);
+                }
+            } catch (Exception e) {
+                LOGGER.error("Error running the command ({}). Exception: {}", command, e.getMessage());
+            }
+        }
+    }
+
     public void setParentGroupId(final String parentGroupId) {
         this.parentGroupId = parentGroupId;
     }