反序列化傑克遜通過使用密鑰值

Question

我有一個類似的JSON結構：

"teams": { 
    "team1Id": "team1Name", 
    "team2Id": "team2Name" 
} 

，我想將其反序列化到這些Java類：

class Teams { 
Team team1; 
Team team2; 
} 

class Team { 
String id; 
String name; 
} 

正如你所看到的應該將作爲JSON密鑰的team1Id和team2Id轉換爲Java字段的值。此外，第一個teamId/teamName對應該歸入存儲在team1中的對象，而第二個對存儲在team2字段中。

是否有任何本機JACKSON映射器來做到這一點，或者我需要爲此創建自己的定製解串器？

Answer 1

您可以爲這個類實現自定義的反序列化器，但是，我認爲，更簡單的解決方案將使用@JsonAnySetter註釋。

class Teams { 

    Team team1 = new Team(); 
    Team team2 = new Team(); 

    @JsonAnySetter 
    public void anySetter(String key, String value) { 
     if (key.startsWith("team1")) { 
      team1.setId(key); 
      team1.setName(value); 
     } else if (key.startsWith("team2")) { 
      team2.setId(key); 
      team2.setName(value); 
     } 
    } 

    //getters, setterr, toString() 
} 

實例：

import java.io.File; 
import java.io.IOException; 

import com.fasterxml.jackson.annotation.JsonAnySetter; 
import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonProgram { 

    public static void main(String[] args) throws IOException { 
     ObjectMapper mapper = new ObjectMapper(); 
     Wrapper wrapper = mapper.readValue(new File("X:/json"), Wrapper.class); 
     System.out.println(wrapper.getTeams()); 
    } 
} 

class Wrapper { 

    private Teams teams; 

    public Teams getTeams() { 
     return teams; 
    } 

    public void setTeams(Teams teams) { 
     this.teams = teams; 
    } 
} 

以上程序打印：

Teams [team1=Team [id=team1Id, name=team1Name], team2=Team [id=team2Id, name=team2Name]] 

此JSON：

{ 
    "teams": { 
     "team1Id": "team1Name", 
     "team2Id": "team2Name" 
    } 
} 

### EDIT 1 ###

如果你的JSON看起來像這樣：

{ 
    "teams": { 
     "12345": "Chelsea", 
     "67890": "Tottenham" 
    } 
} 

我建議把它反序列化到LinkedHashMap<String, String>，之後將其轉換爲Teams對象。示例程序：

import java.io.File; 
import java.io.IOException; 
import java.util.ArrayList; 
import java.util.LinkedHashMap; 
import java.util.List; 
import java.util.Map.Entry; 

import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonProgram { 

    public static void main(String[] args) throws IOException { 
     ObjectMapper mapper = new ObjectMapper(); 
     Wrapper wrapper = mapper.readValue(new File("X:/json"), Wrapper.class); 
     System.out.println(wrapper.toTeams()); 
    } 
} 

class Wrapper { 

    private LinkedHashMap<String, String> teams; 

    public LinkedHashMap<String, String> getTeams() { 
     return teams; 
    } 

    public void setTeams(LinkedHashMap<String, String> teams) { 
     this.teams = teams; 
    } 

    public Teams toTeams() { 
     List<Team> teamList = toTeamList(); 

     Teams result = new Teams(); 
     result.setTeam1(teamList.get(0)); 
     result.setTeam2(teamList.get(1)); 
     return result; 
    } 

    private List<Team> toTeamList() { 
     List<Team> teamList = new ArrayList<Team>(teams.size()); 
     for (Entry<String, String> entry : teams.entrySet()) { 
      Team team = new Team(); 
      team.setId(entry.getKey()); 
      team.setName(entry.getValue()); 
      teamList.add(team); 
     } 

     return teamList; 
    } 
} 

上面的程序打印：

Teams [team1=Team [id=12345, name=Chelsea], team2=Team [id=67890, name=Tottenham]]