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156 lines
5 KiB
Go
156 lines
5 KiB
Go
// Copyright 2018 Frank Schroeder. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package properties provides functions for reading and writing
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// ISO-8859-1 and UTF-8 encoded .properties files and has
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// support for recursive property expansion.
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//
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// Java properties files are ISO-8859-1 encoded and use Unicode
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// literals for characters outside the ISO character set. Unicode
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// literals can be used in UTF-8 encoded properties files but
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// aren't necessary.
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//
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// To load a single properties file use MustLoadFile():
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//
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// p := properties.MustLoadFile(filename, properties.UTF8)
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//
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// To load multiple properties files use MustLoadFiles()
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// which loads the files in the given order and merges the
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// result. Missing properties files can be ignored if the
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// 'ignoreMissing' flag is set to true.
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//
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// Filenames can contain environment variables which are expanded
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// before loading.
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//
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// f1 := "/etc/myapp/myapp.conf"
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// f2 := "/home/${USER}/myapp.conf"
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// p := MustLoadFiles([]string{f1, f2}, properties.UTF8, true)
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//
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// All of the different key/value delimiters ' ', ':' and '=' are
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// supported as well as the comment characters '!' and '#' and
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// multi-line values.
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//
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// ! this is a comment
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// # and so is this
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//
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// # the following expressions are equal
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// key value
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// key=value
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// key:value
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// key = value
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// key : value
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// key = val\
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// ue
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//
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// Properties stores all comments preceding a key and provides
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// GetComments() and SetComments() methods to retrieve and
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// update them. The convenience functions GetComment() and
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// SetComment() allow access to the last comment. The
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// WriteComment() method writes properties files including
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// the comments and with the keys in the original order.
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// This can be used for sanitizing properties files.
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//
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// Property expansion is recursive and circular references
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// and malformed expressions are not allowed and cause an
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// error. Expansion of environment variables is supported.
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//
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// # standard property
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// key = value
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//
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// # property expansion: key2 = value
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// key2 = ${key}
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//
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// # recursive expansion: key3 = value
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// key3 = ${key2}
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//
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// # circular reference (error)
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// key = ${key}
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//
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// # malformed expression (error)
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// key = ${ke
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//
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// # refers to the users' home dir
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// home = ${HOME}
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//
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// # local key takes precedence over env var: u = foo
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// USER = foo
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// u = ${USER}
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//
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// The default property expansion format is ${key} but can be
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// changed by setting different pre- and postfix values on the
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// Properties object.
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//
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// p := properties.NewProperties()
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// p.Prefix = "#["
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// p.Postfix = "]#"
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//
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// Properties provides convenience functions for getting typed
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// values with default values if the key does not exist or the
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// type conversion failed.
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//
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// # Returns true if the value is either "1", "on", "yes" or "true"
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// # Returns false for every other value and the default value if
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// # the key does not exist.
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// v = p.GetBool("key", false)
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//
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// # Returns the value if the key exists and the format conversion
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// # was successful. Otherwise, the default value is returned.
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// v = p.GetInt64("key", 999)
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// v = p.GetUint64("key", 999)
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// v = p.GetFloat64("key", 123.0)
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// v = p.GetString("key", "def")
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// v = p.GetDuration("key", 999)
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//
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// As an alternative properties may be applied with the standard
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// library's flag implementation at any time.
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//
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// # Standard configuration
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// v = flag.Int("key", 999, "help message")
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// flag.Parse()
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//
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// # Merge p into the flag set
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// p.MustFlag(flag.CommandLine)
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//
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// Properties provides several MustXXX() convenience functions
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// which will terminate the app if an error occurs. The behavior
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// of the failure is configurable and the default is to call
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// log.Fatal(err). To have the MustXXX() functions panic instead
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// of logging the error set a different ErrorHandler before
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// you use the Properties package.
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//
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// properties.ErrorHandler = properties.PanicHandler
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//
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// # Will panic instead of logging an error
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// p := properties.MustLoadFile("config.properties")
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//
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// You can also provide your own ErrorHandler function. The only requirement
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// is that the error handler function must exit after handling the error.
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//
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// properties.ErrorHandler = func(err error) {
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// fmt.Println(err)
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// os.Exit(1)
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// }
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//
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// # Will write to stdout and then exit
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// p := properties.MustLoadFile("config.properties")
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//
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// Properties can also be loaded into a struct via the `Decode`
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// method, e.g.
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//
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// type S struct {
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// A string `properties:"a,default=foo"`
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// D time.Duration `properties:"timeout,default=5s"`
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// E time.Time `properties:"expires,layout=2006-01-02,default=2015-01-01"`
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// }
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//
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// See `Decode()` method for the full documentation.
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//
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// The following documents provide a description of the properties
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// file format.
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//
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// http://en.wikipedia.org/wiki/.properties
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//
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// http://docs.oracle.com/javase/7/docs/api/java/util/Properties.html#load%28java.io.Reader%29
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//
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package properties
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