config: add more method

DefaultString(key string, defaultval string) string      // support
section::key type in key string when using ini and json type;
Int,Int64,Bool,Float,DIY are same.
	DefaultStrings(key string, defaultval []string) []string //get string
slice
	DefaultInt(key string, defaultval int) int
	DefaultInt64(key string, defaultval int64) int64
	DefaultBool(key string, defaultval bool) bool
	DefaultFloat(key string, defaultval float64) float64
	DIY(key string) (interface{}, error)
	GetSection(section string) (map[string]string, error)
	SaveConfigFile(filename string) error

config/xml/xml.go

@@ -10,12 +10,16 @@
 package xml
 
 import (
+	"encoding/xml"
 	"errors"
+	"fmt"
 	"io/ioutil"
 	"os"
+	"path"
 	"strconv"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/astaxie/beego/config"
 	"github.com/beego/x2j"
@@ -49,6 +53,16 @@ func (xc *XMLConfig) Parse(filename string) (config.ConfigContainer, error) {
 	return x, nil
 }
 
+func (x *XMLConfig) ParseData(data []byte) (config.ConfigContainer, error) {
+	// Save memory data to temporary file
+	tmpName := path.Join(os.TempDir(), "beego", fmt.Sprintf("%d", time.Now().Nanosecond()))
+	os.MkdirAll(path.Dir(tmpName), os.ModePerm)
+	if err := ioutil.WriteFile(tmpName, data, 0655); err != nil {
+		return nil, err
+	}
+	return x.Parse(tmpName)
+}
+
 // A Config represents the xml configuration.
 type XMLConfigContainer struct {
 	data map[string]interface{}
@@ -60,21 +74,61 @@ func (c *XMLConfigContainer) Bool(key string) (bool, error) {
 	return strconv.ParseBool(c.data[key].(string))
 }
 
+// DefaultBool return the bool value if has no error
+// otherwise return the defaultval
+func (c *XMLConfigContainer) DefaultBool(key string, defaultval bool) bool {
+	if v, err := c.Bool(key); err != nil {
+		return defaultval
+	} else {
+		return v
+	}
+}
+
 // Int returns the integer value for a given key.
 func (c *XMLConfigContainer) Int(key string) (int, error) {
 	return strconv.Atoi(c.data[key].(string))
 }
 
+// DefaultInt returns the integer value for a given key.
+// if err != nil return defaltval
+func (c *XMLConfigContainer) DefaultInt(key string, defaultval int) int {
+	if v, err := c.Int(key); err != nil {
+		return defaultval
+	} else {
+		return v
+	}
+}
+
 // Int64 returns the int64 value for a given key.
 func (c *XMLConfigContainer) Int64(key string) (int64, error) {
 	return strconv.ParseInt(c.data[key].(string), 10, 64)
 }
 
+// DefaultInt64 returns the int64 value for a given key.
+// if err != nil return defaltval
+func (c *XMLConfigContainer) DefaultInt64(key string, defaultval int64) int64 {
+	if v, err := c.Int64(key); err != nil {
+		return defaultval
+	} else {
+		return v
+	}
+}
+
 // Float returns the float value for a given key.
 func (c *XMLConfigContainer) Float(key string) (float64, error) {
 	return strconv.ParseFloat(c.data[key].(string), 64)
 }
 
+// DefaultFloat returns the float64 value for a given key.
+// if err != nil return defaltval
+func (c *XMLConfigContainer) DefaultFloat(key string, defaultval float64) float64 {
+	if v, err := c.Float(key); err != nil {
+		return defaultval
+	} else {
+		return v
+	}
+}
+
 // String returns the string value for a given key.
 func (c *XMLConfigContainer) String(key string) string {
 	if v, ok := c.data[key].(string); ok {
@@ -83,11 +137,56 @@ func (c *XMLConfigContainer) String(key string) string {
 	return ""
 }
 
+// DefaultString returns the string value for a given key.
+// if err != nil return defaltval
+func (c *XMLConfigContainer) DefaultString(key string, defaultval string) string {
+	if v := c.String(key); v == "" {
+		return defaultval
+	} else {
+		return v
+	}
+}
+
 // Strings returns the []string value for a given key.
 func (c *XMLConfigContainer) Strings(key string) []string {
 	return strings.Split(c.String(key), ";")
 }
 
+// DefaultStrings returns the []string value for a given key.
+// if err != nil return defaltval
+func (c *XMLConfigContainer) DefaultStrings(key string, defaultval []string) []string {
+	if v := c.Strings(key); len(v) == 0 {
+		return defaultval
+	} else {
+		return v
+	}
+}
+
+// GetSection returns map for the given section
+func (c *XMLConfigContainer) GetSection(section string) (map[string]string, error) {
+	if v, ok := c.data[section]; ok {
+		return v.(map[string]string), nil
+	} else {
+		return nil, errors.New("not exist setction")
+	}
+}
+
+// SaveConfigFile save the config into file
+func (c *XMLConfigContainer) SaveConfigFile(filename string) (err error) {
+	// Write configuration file by filename.
+	f, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	b, err := xml.MarshalIndent(c.data, "  ", "    ")
+	if err != nil {
+		return err
+	}
+	_, err = f.Write(b)
+	return err
+}
+
 // WriteValue writes a new value for key.
 func (c *XMLConfigContainer) Set(key, val string) error {
 	c.Lock()