plugin ファイルは src/main/resources/META-INF/services/ に配置

JacksonJsonProvider.java

package org.seasar.cubby.plugins.jackson.spi;

import java.io.IOException;

import org.codehaus.jackson.map.ObjectMapper;
import org.seasar.cubby.spi.ContainerProvider;
import org.seasar.cubby.spi.JsonProvider;
import org.seasar.cubby.spi.ProviderFactory;
import org.seasar.cubby.spi.container.Container;
import org.seasar.cubby.spi.container.LookupException;
import org.slf4j.LoggerFactory;

public class JacksonJsonProvider implements JsonProvider {

    private ObjectMapper mapper;

    @Override
    public String toJson(final Object o) {
        if (mapper == null) {
            mapper = createObjectMapper();
        }

        try {
            return mapper.writeValueAsString(o);
        } catch (IOException e) {
            LoggerFactory.getLogger(this.getClass()).error(e.getMessage(), e);
            return null;
        }
    }

    private ObjectMapper createObjectMapper() {
        final Container container = ProviderFactory.get(ContainerProvider.class).getContainer();
        try {
            return container.lookup(ObjectMapper.class);
        } catch (final LookupException e) {
            return new ObjectMapper();
        }
    }
}

JacksonPlugin.java

package org.seasar.cubby.plugins.jackson;

import org.seasar.cubby.plugin.AbstractPlugin;
import org.seasar.cubby.plugins.jackson.spi.JacksonJsonProvider;
import org.seasar.cubby.spi.JsonProvider;
import org.seasar.cubby.spi.Provider;

public class JacksonPlugin extends AbstractPlugin {

    /** JSON のプロバイダ。 */
    private final JsonProvider jsonProvider = new JacksonJsonProvider();

    /**
     * インスタンス化します。
     */
    public JacksonPlugin() {
        support(JsonProvider.class);
    }

    /**
     * {@inheritDoc}
     */
    public <S extends Provider> S getProvider(final Class<S> service) {
        if (JsonProvider.class.equals(service)) {
            return service.cast(jsonProvider);
        }
        return null;
    }
}

org.seasar.cubby.plugin.Plugin

org.seasar.cubby.plugins.jackson.JacksonPlugin