Golang : delete and modify XML file content



Tags : golang XML

In our two previous tutorials on how to read XML file and how to create XML file, we have forgotten to show you how to modify and delete XML content :P In this tutorial, we will use the standard library function to achieve the followings : Read an existing XML file(Employees.xml) Map the data to structs Add one new record Delete one record from the map Update the new record Save the date to a new XML file(LatestEmployees.xml) Employees.xml <?xml version="1.0"?> <company> <staff> <id>101</id> <firstname>Derek</firstname> <lastname>Young</lastname> <username>derekyoung</username> </staff> <staff> <id>102</id> <firstname>John</firstname> <lastname>Smith</lastname> <username>johnsmith</username> </staff> </company> This is the full source code : modifyxml.go package main import ( "fmt" "io/ioutil" "os" "encoding/xml" "io" ) type Staff struct { XMLName xml.Name `xml:"staff"` ID int `xml:"id"` FirstName string `xml:"firstname"` LastName string `xml:"lastname"` UserName string `xml:"username"` var staffmap map[string]Staff type Company struct { XMLName xml.Name `xml:"company"` Staffs []Staff `xml:"staff"` func (s Staff) String() string { return fmt.Sprintf("\t ID : %d - FirstName : %s - LastName : %s - UserName : %s \n", s.ID, s.FirstName , s.LastName, s.UserName) func (s Staff) IDnum() int { return s.ID func (s Staff) FName() string { return s.FirstName func (s Staff) LName() string { return s.LastName func (s Staff) UName() string { return s.UserName func main() { xmlFile, err := os.Open("Employees.xml") if err != nil { fmt.Println("Error opening file:", err) return defer xmlFile.Close() XMLdata, _ := ioutil.ReadAll(xmlFile) var c Company xml.Unmarshal(XMLdata, &c) // add one new record - we will modify this record in the map later c.Staffs = append(c.Staffs, Staff{ID: 103, FirstName: "Adam", LastName: "Ng", UserName: "huh?") staffmap = make(map[string]Staff) // populate the map for _, staff := range c.Staffs { staffmap[staff.FName()] = Staff{ID : staff.IDnum(), FirstName : staff.FName(), LastName : staff.LName(), UserName : staff.UName() fmt.Println("Map BEFORE delete operation :") fmt.Println(staffmap) delete(staffmap,"Derek") // remove Derek from staffs fmt.Println("Map AFTER delete operation :") fmt.Println(staffmap) // modify staffmap["Adam"] - change ID to 108 and fix the huh? username staffmap["Adam"] = Staff{ID: 108, FirstName: "Adam", LastName: "Ng", UserName: "adamng" fmt.Println("Map AFTER UPDATE operation :") fmt.Println(staffmap) // write to LatestEmployees.xml v := &Company{ for _, i := range staffmap { v.Staffs = append(v.Staffs, staffmap[i.FName()]) // remember we declared map[string]Staff above filename := "LatestEmployees.xml" file, _ := os.Create(filename) xmlWriter := io.Writer(file) encoder := xml.NewEncoder(xmlWriter) encoder.Indent(" ", " ") if err := encoder.Encode(v); err != nil { fmt.Printf("error : %v\n", err) encoder.Flush() fmt.Printf("Write operation to %s completed\n", filename) Executing modifyxml.go will produce the following output : Map BEFORE delete operation : map[Derek: ID : 101 - FirstName : Derek - LastName : Young - UserName : derekyoung John: ID : 102 - FirstName : John - LastName : Smith - UserName : johnsmith Adam: ID : 103 - FirstName : Adam - LastName : Ng - UserName : huh? ] Map AFTER delete operation : map[Adam: ID : 103 - FirstName : Adam - LastName : Ng - UserName : huh? John: ID : 102 - FirstName : John - LastName : Smith - UserName : johnsmith ] Map AFTER UPDATE operation : map[John: ID : 102 - FirstName : John - LastName : Smith - UserName : johnsmith Adam: ID : 108 - FirstName : Adam - LastName : Ng - UserName : adamng ] Write operation to LatestEmployees.xml completed and the content of LatestEmployees.xml : <company> <staff> <id>102</id> <firstname>John</firstname> <lastname>Smith</lastname> <username>johnsmith</username> </staff> <staff> <id>108</id> <firstname>Adam</firstname> <lastname>Ng</lastname> <username>adamng</username> </staff> </company> Hope this tutorial will be helpful to those learning Go and XML. Note : There should be better 3rd party solution to handle XML file in Golang. This tutorial uses the standard library.


Tags : golang XML

By Adam Ng

IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.


Advertisement

Advertisement