AbstractContent.java

/*
 * AbstractContent
 */
package gov.usgs.earthquake.product;

import java.io.OutputStream;
import java.security.DigestOutputStream;
import java.security.MessageDigest;
import java.util.Base64;
import java.util.Date;

import gov.usgs.earthquake.util.NullOutputStream;
import gov.usgs.util.StreamUtils;

/**
 * AbstractContent is a base class for other content classes and implements
 * common functionality.
 */
public abstract class AbstractContent implements Content {

    /** The content mime type. */
    private String contentType;

    /** When this content was created. */
    private Date lastModified;

    /** How much content there is. */
    private Long length;

    /** Base64 encoded hash of content */
    String sha256;

    /**
     * Null values are replaced with defaults.
     *
     * @param contentType
     *            defaults to "text/plain".
     * @param lastModified
     *            defaults to new Date().
     * @param length
     *            defaults to -1L.
     */
    public AbstractContent(final String contentType, final Date lastModified,
            final Long length) {
        setContentType(contentType);
        setLastModified(lastModified);
        setLength(length);
    }

    /**
     * Copy constructor from another content.
     *
     * @param content
     *            the content to copy.
     */
    public AbstractContent(final Content content) {
        this(content.getContentType(), content.getLastModified(), content
                .getLength());
    }

    /**
     * Default Constructor which requires no arguments. Default values are used
     * for all fields.
     */
    public AbstractContent() {
        this(null, null, null);
    }

    /**
     * @return the content mime type.
     */
    public String getContentType() {
        return contentType;
    }

    /**
     * Set the content mime type.
     *
     * @param contentType
     *            the content mime type.
     */
    public void setContentType(final String contentType) {
        if (contentType == null) {
            this.contentType = "text/plain";
        } else {
            this.contentType = contentType;
        }
    }

    /**
     * @return the content creation date.
     */
    public Date getLastModified() {
        return lastModified;
    }

    /**
     * Set when this content was created.
     *
     * @param lastModified
     *            when this content was created.
     */
    public void setLastModified(final Date lastModified) {
        if (lastModified == null) {
            this.lastModified = new Date();
        } else {
            this.lastModified = new Date(lastModified.getTime());
        }

        // Round to nearest second. Some file systems do not preserve
        // milliseconds.
        this.lastModified
                .setTime((this.lastModified.getTime() / 1000L) * 1000L);
    }

    /**
     * @return the content length, or -1 if unknown.
     */
    public Long getLength() {
        return length;
    }

    /**
     * Set the content length.
     *
     * @param length long to set
     */
    public void setLength(final Long length) {
        if (length == null) {
            this.length = -1L;
        } else {
            this.length = length;
        }
    }


    /** Get the Sha256 hash. */
    @Override
    public String getSha256() throws Exception {
        return getSha256(true);
    }

    /**
     * Get or generate the MD5 hash of content.
     *
     * @param computeIfMissing Use getInputStream to generate hash if missing.
     * @return sha256 string
     * @throws Exception if error occurs
     */
    public String getSha256(final boolean computeIfMissing) throws Exception {
        if (sha256 == null && computeIfMissing) {
            try (final DigestOutputStream contentDigest =
                            new DigestOutputStream(new NullOutputStream(), MessageDigest.getInstance("SHA-256"));
                    final OutputStream unclosable = new StreamUtils.UnclosableOutputStream(contentDigest)) {
                StreamUtils.transferStream(this.getInputStream(), unclosable);
                contentDigest.flush();
                setSha256(Base64.getEncoder().encodeToString(contentDigest.getMessageDigest().digest()));
            }
        }
        return sha256;
    }

    /**
     * Set the sha256 hash of content.
     *
     * @param sha256 to set
     */
    public void setSha256(final String sha256) {
        this.sha256 = sha256;
    }
}