How to use custom cache implementation Leave feedback

Implementing Memory Cache

In this section we build the custom MemoryCache class that is based on HashMap and demonstrate how to use it in GroupDocs.Viewer.

The complete listing of the MemoryCache.java file is below:

Java

import com.groupdocs.viewer.caching.Cache;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MemoryCache implements Cache {
    private final Map<String, Object> data = new HashMap<>();
    private final String mPrefix;

    public MemoryCache(String prefix) {
        this.mPrefix = prefix;
    }

    @Override
    public void set(String key, Object value) {
        data.put(mPrefix + key, value);
    }

    @Override
    public Object get(String key) {
        return data.get(mPrefix + key);
    }

    @Override
    public List<String> getKeys(String filter) {
        List<String> result = new ArrayList<>();
        for (String key : data.keySet()) {
            if (key.contains(filter)) {
                result.add(key);
            }
        }
        return result;
    }
}

Example usage of MemoryCache type.

Java

import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.ViewerSettings;
import com.groupdocs.viewer.options.HtmlViewOptions;
// ...

MemoryCache memoryCache = new MemoryCache("cache-key-prefix-");
ViewerSettings viewerSettings = new ViewerSettings(memoryCache);

try (Viewer viewer = new Viewer("sample.docx", viewerSettings)) {
    HtmlViewOptions options = HtmlViewOptions.forEmbeddedResources();

    long currentTimeMillis = System.currentTimeMillis();
    viewer.view(options);
    currentTimeMillis = System.currentTimeMillis() - currentTimeMillis;
    System.out.println("Time taken on first call to View method " + currentTimeMillis + " (ms).");

    currentTimeMillis = System.currentTimeMillis();
    viewer.view(options);
    currentTimeMillis = System.currentTimeMillis() - currentTimeMillis;
    System.out.println("Time taken on second call to View method " + currentTimeMillis + " (ms).");
}

After running the code above the similar output will be printed in a console:

Using Custom Model Classes for Caching

Default Viewer models implements the serializable interface. But you may want to use other library for serialization. Lots of them want you to annotate classes and fields of classes that should be serialized. You can create custom models with appropriate fields and configure GroupDocs.Viewer to use these models.

To do this, follow these steps:

Create custom models, implementing Viewer model’s interfaces, like ViewInfo, FileInfo, and so on (see full list of interfaces in the CacheableFactory class).
Create custom model factory (CustomFactory) extending class CacheableFactory. Each method in the class must be overridden to return the instance of your cache model.
Configure GroupDocs.Viewer to use the CustomFactory using the CacheableFactory.setInstance(new CustomFactory()) method before creating the Viewer object.
Configure the GroupDocs.Viewer cache as usual. GroupDocs.Viewer put your model’s objects into the set method of the cache implementation so you can serialize it in any way.

Java

public class CustomFileInfoJackson implements FileInfo {
    @JsonProperty("FileType")
    private final String mFileType;
    @JsonProperty("Encrypted")
    private boolean mEncrypted;

    @JsonCreator
    public CustomFileInfoJackson(@JsonProperty("FileType") String fileType) {
        mFileType = fileType;
    }

    @Override
    public FileType getFileType() {
        return FileType.valueOf(mFileType);
    }

    @Override
    public boolean isEncrypted() {
        return mEncrypted;
    }

    @Override
    public void setEncrypted(boolean encrypted) {
        mEncrypted = encrypted;
    }
}

Java

public class CustomFactory extends CacheableFactory {

    //...

    @Override
    public FileInfo newFileInfo(FileType fileType) {
        return new CustomFileInfoJackson(fileType.name());
    }

    //...

}

Java

public class JacksonCache implements Cache {

    //...

    @Override
    public void set(String key, Object value) {
        final byte[] bytes;
        if (value instanceof InputStream) {
            bytes = IOUtils.toByteArray((InputStream) value);
        } else {
            // Serialize in any way
            bytes = jacksonMapper.writeValueAsBytes(value);
        }
        // Here bytes could be written to file or sent somewhere
        mData.put(key, bytes);
    }

    //...

    @Override
    public <T> T get(String key, Class<T> clazz) {
        final byte[] bytes = mData.get(key);
        if (InputStream.class.equals(clazz)) {
            return (T) new ByteArrayInputStream(bytes);
        } else {
            // Deserialize in any way
            return jacksonMapper.readValue(bytes, clazz);
        }
    }

    //...

}

Java

import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.ViewerSettings;
import com.groupdocs.viewer.caching.Cache;
import com.groupdocs.viewer.caching.extra.CacheableFactory;
// ...

CacheableFactory.setInstance(new CustomFactory());

Cache cache = new JacksonCache();
ViewerSettings settings = new ViewerSettings(cache);
try (Viewer viewer = new Viewer("document.doc", settings)) {
    // Do work
}

We value your opinion. Your feedback will help us improve our documentation.

How to use custom cache implementation Leave feedback

On this page

Implementing Memory Cache

Using Custom Model Classes for Caching

Was this page helpful?

Any additional feedback you'd like to share with us?

Please tell us how we can improve this page.

Thank you for your feedback!

On this page