User Interface for GroupDocs.Viewer for Java. API for easily integrating a document viewer into 3rd-party projects.

1. Add GroupDocs Maven repository

       <repositories>
           <repository>
               <id>releases.groupdocs.com</id>
               <name>releases.groupdocs</name>
               <url>https://releases.groupdocs.com/java/repo/</url>
           </repository>
       </repositories>

2. Add required dependencies

    <dependencies>
      <dependency>
        <groupId>com.groupdocs</groupId>
        <artifactId>groupdocs-viewer-ui</artifactId>
        <version>25.2</version>
      </dependency>
   
      <dependency>
        <groupId>com.groupdocs</groupId>
        <artifactId>groupdocs-viewer</artifactId>
        <version>25.2</version>
      </dependency>
      <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.13.4.1</version>
      </dependency>
      <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.13.3</version>
      </dependency>
    </dependencies>

3. Configure GroupDocs.Viewer UI

   @Configuration
   public class ViewerConfiguration {
   public static final String VIEWER_UI_PATH = "/viewer";
   
      public static final String VIEWER_API_ENDPOINT = "/viewer-api";
   
      private JakartaViewerEndpointHandler _viewerEndpointHandler;
   
      @PostConstruct
      public void init() {
          _viewerEndpointHandler = JakartaViewerEndpointHandler
                  .setupGroupDocsViewer((viewerConfig, config) -> {
                      final ViewerType viewerType = ViewerType.PNG;
   
                     viewerConfig.setViewerType(viewerType);
                     // viewerConfig.setLicensePath("GroupDocs.Viewer.Product.Family.lic");
   
                      config.setPreloadPages(2);
                      config.setBaseUrl("http://127.0.0.1:8080");
                      config.setRenderingMode(viewerType.toRenderingMode());
                  })
   
                  .setupGroupDocsViewerUI(uiOptions -> {
                      uiOptions.setUiPath(VIEWER_UI_PATH);
                  })
                  .setupGroupDocsViewerApi(apiOptions -> {
                      apiOptions.setApiEndpoint(VIEWER_API_ENDPOINT);
                  })
                  .setupLocalStorage(Paths.get("./").toAbsolutePath())
                  .setupInMemoryCache(inMemoryCacheConfig -> {
                      inMemoryCacheConfig.setGroupCacheEntriesByFile(false);
                      inMemoryCacheConfig.setCacheEntryExpirationTimeoutMinutes(3);
                  })
      //			.setupLocalCache(cacheConfig -> {
      //				cacheConfig.setCachePath(Paths.get("/home/user/cache"));
      //			})
          ;
      }
   
      @Bean
      public JakartaViewerEndpointHandler viewerEndpointHandler() {
          return _viewerEndpointHandler;
      }
   }

4. Create a controller that will handle viewer requests

   @Controller
   public class ViewerController {
   	private final JakartaViewerEndpointHandler _viewerEndpointHandler;
   
   	public ViewerController(JakartaViewerEndpointHandler endpointHandler) {
   		this._viewerEndpointHandler = endpointHandler;
   	}
   
   	@GetMapping({ ViewerConfiguration.VIEWER_UI_PATH, ViewerConfiguration.VIEWER_UI_PATH + "/**",
   			ViewerConfiguration.VIEWER_API_ENDPOINT, ViewerConfiguration.VIEWER_API_ENDPOINT + "/**" })
   	public void handleViewerUiRequest(HttpServletRequest request, HttpServletResponse response) {
   		this._viewerEndpointHandler.handleViewerRequest(request, response);
   	}
   
   	@PostMapping({ ViewerConfiguration.VIEWER_API_ENDPOINT, ViewerConfiguration.VIEWER_API_ENDPOINT + "/**" })
   	public void handleViewerApiRequest(HttpServletRequest request, HttpServletResponse response) {
   		this._viewerEndpointHandler.handleViewerRequest(request, response);
   	}
   }

5. Run application and open http://127.0.0.1:8080/viewer (/viewer part is from VIEWER_UI_PATH)

Optionally you can enable logging by adding logback.xml file to src/main/resources directory. Example of the file:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

	<property name="LOGS" value="./logs" />

	<appender name="Console"
			  class="ch.qos.logback.core.ConsoleAppender">
		<layout class="ch.qos.logback.classic.PatternLayout">
			<Pattern>
				%black(%d{ISO8601}) %highlight(%-5level) [%blue(%t)] %yellow(%C{1}): %msg%n%throwable
			</Pattern>
		</layout>
	</appender>

	<appender name="RollingFile"
			  class="ch.qos.logback.core.rolling.RollingFileAppender">
		<file>${LOGS}/spring-boot-logger.log</file>
		<encoder
			class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
			<Pattern>%d %p %C{1} [%t] %m%n</Pattern>
		</encoder>

		<rollingPolicy
			class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
			<!-- rollover daily and when the file reaches 10 MegaBytes -->
			<fileNamePattern>${LOGS}/archived/spring-boot-logger-%d{yyyy-MM-dd}.%i.log
			</fileNamePattern>
			<timeBasedFileNamingAndTriggeringPolicy
				class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
				<maxFileSize>10MB</maxFileSize>
			</timeBasedFileNamingAndTriggeringPolicy>
		</rollingPolicy>
	</appender>

	<!-- LOG everything at INFO level -->
	<root level="info">
		<appender-ref ref="RollingFile" />
		<appender-ref ref="Console" />
	</root>

	<!-- LOG "com.baeldung*" at TRACE level -->
	<logger name="com.groupdocs" level="debug" additivity="false">
		<appender-ref ref="RollingFile" />
		<appender-ref ref="Console" />
	</logger>

</configuration>

In case of getting next error

error: error reading /home/jenkins/groupdocs-viewer.jar; Unsupported size: 19732345 for JarEntry META-INF/MANIFEST.MF. Allowed max size: 8000000 bytes

Create environment variables MAVEN_OPTS, JAVA_OPTS or JAVA_TOOL_OPTIONS with value -Djdk.jar.maxSignatureFileSize=25000000. Which variable to use depends on your project and way you run it.