Summary

The ZIP file system provider is enhanced to support creating the file system in read-only mode.

Problem

A java.nio.file.FileSystem can be read-only or read-write. A read-only FileSystem does not allow applications to change the contents of the FileSystem.

The ZIP file system provider treats the contents of a ZIP or JAR file as a file system. When a ZIP file system is constructed for a multi-release JAR file and the "releaseVersion" property is set to a valid non-null value, the implementation in ZIP file system marks the file system as read-only, thus disallowing updates to the underlying JAR file.

Similarly, when the underlying ZIP/JAR file is not writable, then the ZIP file system implementation marks the file system as read-only.

Except for these two cases, there currently is no explicit way for applications to instruct the ZIP file system provider to construct a ZIP file system as read-only.

Solution

The ZIP file system provider implementation is enhanced to support a new accessMode environmental parameter. This new parameter allows applications to explicitly construct a ZIP file system in read-write or read-only mode.

Specification

src/jdk.zipfs/share/classes/module-info.java

 *   <td>
- *       If the value is {@code true}, the ZIP file system provider
- *       creates a new ZIP or JAR file if it does not exist.
+ *       If the value is {@code true}, the ZIP file system provider creates a
+ *       new ZIP or JAR file if it does not exist.
  *   </td>
  * </tr>
  * <tr>


  *           </li>
  *           <li>
  *               If the value is not {@code "STORED"} or {@code "DEFLATED"}, an
- *               {@code IllegalArgumentException} will be thrown when the Zip
- *               filesystem is created.
+ *               {@code IllegalArgumentException} will be thrown when creating the
+ *               ZIP file system.
  *           </li>
  *       </ul>
  *   </td>


  *           <li>
  *               If the value does not represent a valid
  *               {@linkplain Runtime.Version Java SE Platform version number},
- *               an {@code IllegalArgumentException} will be thrown.
+ *               an {@code IllegalArgumentException} will be thrown when creating
+ *               the ZIP file system.
  *           </li>
  *       </ul>
  *   </td>
  * </tr>
+ * <tr>
+ *   <th scope="row">accessMode</th>
+ *   <td>{@link java.lang.String}</td>
+ *   <td>null/unset</td>
+ *   <td>
+ *       A value defining the desired access mode of the file system.
+ *       ZIP file systems can be created to allow for <em>read-write</em> or
+ *       <em>read-only</em> access.
+ *       <ul>
+ *           <li>
+ *               If no value is set, the file system is created <em>read-write</em>
+ *               if possible. Use {@link java.nio.file.FileSystem#isReadOnly()
+ *               isReadOnly()} to determine the actual access mode.
+ *           </li>
+ *           <li>
+ *               If the value is {@code "readOnly"}, the file system is created
+ *               <em>read-only</em>, and {@link java.nio.file.FileSystem#isReadOnly()
+ *               isReadOnly()} will always return {@code true}. Creating a
+ *               <em>read-only</em> file system requires the underlying ZIP file to
+ *               already exist.
+ *               Specifying the {@code create} property as {@code true} with the
+ *               {@code accessMode} as {@code readOnly} will cause an {@code
+ *               IllegalArgumentException} to be thrown when creating the ZIP file
+ *               system.
+ *           </li>
+ *           <li>
+ *               If the value is {@code "readWrite"}, the file system is created
+ *               <em>read-write</em>, and {@link java.nio.file.FileSystem#isReadOnly()
+ *               isReadOnly()} will always return {@code false}. If a writable file
+ *               system cannot be created, an {@code IOException} will be thrown
+ *               when creating the ZIP file system.
+ *           </li>
+ *           <li>
+ *               Any other values will cause an {@code IllegalArgumentException}
+ *               to be thrown when creating the ZIP file system.
+ *           </li>
+ *       </ul>
+ *       The {@code accessMode} property has no effect on reported POSIX file
+ *       permissions (in cases where POSIX support is enabled).
+ *   </td>
+ * </tr>
  * </tbody>
  * </table>