Now, in the following sections, we will be looking at ways to download files from a URL using third-party libraries instead of core Java functionality components. Now you may be thinking why would we use this when Java has its own set of libraries to handle IO operations. However, Apache Commons IO overcomes the problem of code rewriting and helps avoid writing boilerplate code. In order to start using the Apache Commons IO library, you will need to download the jar files from the official website.
When you are done downloading the jar files, you need to add them to use them. If you are using an Integrated Development Environment IDE such as Eclipse , you will need to add the files to the build path of your project.
There is only a single line of code required to download a file, which looks like:. The connection and read timeouts convey the permissible time for which either the connection may stay idle or reading from the URL may stop. We will use the copy inputStream, fileOS method to download a file into the local system.
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The function returns the number of bytes copied. If the value of the variable i is -1, then it indicates that the contents of the file are over 2GB. When the returned value is -1, you can use the function copyLarge inputStream, fileOS in place of the copy inputstream, fileOS function to handle this load. Both of these functions buffer the inputstream internally. The internal buffer means we do not have to use the BufferedInputStream class to enhance our code performance and helps us avoid writing boilerplate code.
Another library managed by the Apache organization is the HttpComponents package. Better use a Servlet for this. Here's a basic example. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 11 years, 2 months ago. Active 11 years, 2 months ago. Viewed 6k times. I have a JSP page that handles file downloads. Implementation Program 1: Program to check if a file or directory physically exist or not.
Then pass these array elements arr[i] to File object and test them to know if they represent a file or directory. Java import java. BufferedReader; import java. File; import java. IOException; import java. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.
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Skip to content. Change Language. Related Articles. Flow Control. Parameters: uri - An absolute, hierarchical URI with a scheme equal to "file" , a non-empty path component, and undefined authority, query, and fragment components Throws: NullPointerException - If uri is null IllegalArgumentException - If the preconditions on the parameter do not hold Since: 1. This is just the last name in the pathname's name sequence.
If the pathname's name sequence is empty, then the empty string is returned. Returns: The name of the file or directory denoted by this abstract pathname, or the empty string if this pathname's name sequence is empty getParent public String getParent Returns the pathname string of this abstract pathname's parent, or null if this pathname does not name a parent directory.
The parent of an abstract pathname consists of the pathname's prefix, if any, and each name in the pathname's name sequence except for the last. If the name sequence is empty then the pathname does not name a parent directory. Returns: The pathname string of the parent directory named by this abstract pathname, or null if this pathname does not name a parent getParentFile public File getParentFile Returns the abstract pathname of this abstract pathname's parent, or null if this pathname does not name a parent directory.
Returns: The abstract pathname of the parent directory named by this abstract pathname, or null if this pathname does not name a parent Since: 1. The resulting string uses the default name-separator character to separate the names in the name sequence.
Returns: The string form of this abstract pathname isAbsolute public boolean isAbsolute Tests whether this abstract pathname is absolute. The definition of absolute pathname is system dependent. Returns: true if this abstract pathname is absolute, false otherwise getAbsolutePath public String getAbsolutePath Returns the absolute pathname string of this abstract pathname. If this abstract pathname is already absolute, then the pathname string is simply returned as if by the getPath method.
If this abstract pathname is the empty abstract pathname then the pathname string of the current user directory, which is named by the system property user. Otherwise this pathname is resolved in a system-dependent way. On UNIX systems, a relative pathname is made absolute by resolving it against the current user directory. On Microsoft Windows systems, a relative pathname is made absolute by resolving it against the current directory of the drive named by the pathname, if any; if not, it is resolved against the current user directory.
Returns: The absolute pathname string denoting the same file or directory as this abstract pathname Throws: SecurityException - If a required system property value cannot be accessed.
Equivalent to new File this. Returns: The absolute abstract pathname denoting the same file or directory as this abstract pathname Throws: SecurityException - If a required system property value cannot be accessed. Since: 1. A canonical pathname is both absolute and unique.
The precise definition of canonical form is system-dependent. This method first converts this pathname to absolute form if necessary, as if by invoking the getAbsolutePath method, and then maps it to its unique form in a system-dependent way. This typically involves removing redundant names such as ". Every pathname that denotes an existing file or directory has a unique canonical form.
Every pathname that denotes a nonexistent file or directory also has a unique canonical form. The canonical form of the pathname of a nonexistent file or directory may be different from the canonical form of the same pathname after the file or directory is created. Similarly, the canonical form of the pathname of an existing file or directory may be different from the canonical form of the same pathname after the file or directory is deleted.
FileDescriptor method denies read access to the file Since: 1. Converts this abstract pathname into a file: URL. The exact form of the URL is system-dependent. If it can be determined that the file denoted by this abstract pathname is a directory, then the resulting URL will end with a slash.
The exact form of the URI is system-dependent. If it can be determined that the file denoted by this abstract pathname is a directory, then the resulting URI will end with a slash. For a given abstract pathname f , it is guaranteed that new File f. Due to the system-dependent nature of abstract pathnames, however, this relationship typically does not hold when a file: URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system.
The authority component is undefined, meaning that it is represented as null. The Path class defines the toUri method to encode the server name in the authority component of the resulting URI. The toPath method may be used to obtain a Path representing this abstract pathname. Returns: An absolute, hierarchical URI with a scheme equal to "file" , a path representing this abstract pathname, and undefined authority, query, and fragment components Throws: SecurityException - If a required system property value cannot be accessed.
On some platforms it may be possible to start the Java virtual machine with special privileges that allow it to read files that are marked as unreadable. Consequently this method may return true even though the file does not have read permissions. Returns: true if and only if the file specified by this abstract pathname exists and can be read by the application; false otherwise Throws: SecurityException - If a security manager exists and its SecurityManager. String method denies read access to the file canWrite public boolean canWrite Tests whether the application can modify the file denoted by this abstract pathname.
On some platforms it may be possible to start the Java virtual machine with special privileges that allow it to modify files that are marked read-only. Consequently this method may return true even though the file is marked read-only. Returns: true if and only if the file system actually contains a file denoted by this abstract pathname and the application is allowed to write to the file; false otherwise.
String method denies write access to the file exists public boolean exists Tests whether the file or directory denoted by this abstract pathname exists. Returns: true if and only if the file or directory denoted by this abstract pathname exists; false otherwise Throws: SecurityException - If a security manager exists and its SecurityManager. String method denies read access to the file or directory isDirectory public boolean isDirectory Tests whether the file denoted by this abstract pathname is a directory.
Returns: true if and only if the file denoted by this abstract pathname exists and is a directory; false otherwise Throws: SecurityException - If a security manager exists and its SecurityManager. String method denies read access to the file isFile public boolean isFile Tests whether the file denoted by this abstract pathname is a normal file. A file is normal if it is not a directory and, in addition, satisfies other system-dependent criteria.
Any non-directory file created by a Java application is guaranteed to be a normal file. Returns: true if and only if the file denoted by this abstract pathname exists and is a normal file; false otherwise Throws: SecurityException - If a security manager exists and its SecurityManager. String method denies read access to the file isHidden public boolean isHidden Tests whether the file named by this abstract pathname is a hidden file. The exact definition of hidden is system-dependent.
On UNIX systems, a file is considered to be hidden if its name begins with a period character '. On Microsoft Windows systems, a file is considered to be hidden if it has been marked as such in the filesystem.
Returns: true if and only if the file denoted by this abstract pathname is hidden according to the conventions of the underlying platform Throws: SecurityException - If a security manager exists and its SecurityManager. String method denies read access to the file Since: 1.
String method denies read access to the file length public long length Returns the length of the file denoted by this abstract pathname. The return value is unspecified if this pathname denotes a directory. Returns: The length, in bytes, of the file denoted by this abstract pathname, or 0L if the file does not exist.
Some operating systems may return 0L for pathnames denoting system-dependent entities such as devices or pipes. String method denies read access to the file createNewFile public boolean createNewFile throws IOException Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist.
The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file. Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead. String method denies write access to the file Since: 1.
If this pathname denotes a directory, then the directory must be empty in order to be deleted. Note that the Files class defines the delete method to throw an IOException when a file cannot be deleted. This is useful for error reporting and to diagnose why a file cannot be deleted. Returns: true if and only if the file or directory is successfully deleted; false otherwise Throws: SecurityException - If a security manager exists and its SecurityManager.
String method denies delete access to the file deleteOnExit public void deleteOnExit Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates. Files or directories are deleted in the reverse order that they are registered.
Invoking this method to delete a file or directory that is already registered for deletion has no effect. Deletion will be attempted only for normal termination of the virtual machine, as defined by the Java Language Specification.
Once deletion has been requested, it is not possible to cancel the request. This method should therefore be used with care. String method denies delete access to the file Since: 1.
If this abstract pathname does not denote a directory, then this method returns null. Otherwise an array of strings is returned, one for each file or directory in the directory. Names denoting the directory itself and the directory's parent directory are not included in the result.
Each string is a file name rather than a complete path.
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