# BlobInfoFactory
Date: 2012-02-24

## com.google.appengine.api.blobstore
Class BlobInfoFactory

    java.lang.Object
      com.google.appengine.api.blobstore.BlobInfoFactory

    public class BlobInfoFactory

extends java.lang.Object

`BlobInfoFactory` provides a trivial interface for retrieving `BlobInfo` metadata.

BlobInfo metadata is stored in read-only `__BlobInfo__` entities in the datastore. This class provides an easy way to access these entities. For more complex queries, you can use the datastore directly.

Field Summary
`static java.lang.String` `CONTENT_TYPE`
`static java.lang.String` `CREATION`
`static java.lang.String` `FILENAME`
`static java.lang.String` `KIND`
`static java.lang.String` `MD5_HASH`
`static java.lang.String` `SIZE`

Constructor Summary
`BlobInfoFactory()` Creates a `BlobInfoFactory` that uses the default implementation of `DatastoreService`.
`BlobInfoFactory(DatastoreService datastoreService)` Creates a `BlobInfoFactory` with the specified implementation of `DatastoreService`.

Method Summary
`BlobInfo` `createBlobInfo(Entity entity)` Creates a `BlobInfo` by extracting content from the specified `Entity`.
`BlobInfo` `loadBlobInfo(BlobKey blobKey)` Loads the `BlobInfo` metadata for `blobKey`.
`java.util.Iterator<BlobInfo>` `queryBlobInfos()` Queries for `BlobInfo` instances, beginning with the `BlobKey` that appears first in lexicographic order.
`java.util.Iterator<BlobInfo>` `queryBlobInfosAfter(BlobKey previousBlob)` Queries for `BlobInfo` instances, beginning at the blob following `previousBlob` in lexicographic order.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### KIND

    public static final java.lang.String KIND

See Also:
  Constant Field Values

### CONTENT_TYPE

    public static final java.lang.String CONTENT_TYPE

See Also:
  Constant Field Values

### CREATION

    public static final java.lang.String CREATION

See Also:
  Constant Field Values

### FILENAME

    public static final java.lang.String FILENAME

See Also:
  Constant Field Values

### SIZE

    public static final java.lang.String SIZE

See Also:
  Constant Field Values

### MD5_HASH

    public static final java.lang.String MD5_HASH

See Also:
  Constant Field Values

Constructor Detail

### BlobInfoFactory

    public BlobInfoFactory()

  Creates a `BlobInfoFactory` that uses the default implementation of `DatastoreService`.

### BlobInfoFactory

    public BlobInfoFactory(DatastoreService datastoreService)

  Creates a `BlobInfoFactory` with the specified implementation of `DatastoreService`.

Method Detail

### loadBlobInfo

    public BlobInfo loadBlobInfo(BlobKey blobKey)

  Loads the `BlobInfo` metadata for `blobKey`. Returns `null` if no matching blob is found.

### queryBlobInfos

    public java.util.Iterator<BlobInfo> queryBlobInfos()

  Queries for `BlobInfo` instances, beginning with the `BlobKey` that appears first in lexicographic order.

### queryBlobInfosAfter

    public java.util.Iterator<BlobInfo> queryBlobInfosAfter(BlobKey previousBlob)

  Queries for `BlobInfo` instances, beginning at the blob following `previousBlob` in lexicographic order. If `previousBlob` is null, the first blob will be returned.

  This is useful for displaying discrete pages of blobs.

### createBlobInfo

    public BlobInfo createBlobInfo(Entity entity)

  Creates a `BlobInfo` by extracting content from the specified `Entity`.