如何控制REST Web Service返回JSON的字段名首字母大写？

Problem Description #

I'm developing a REST Web Service with JAX-RS, and I've defined the AccountSyncResponse entity class and corresponding POST endpoint as follows:

AccountSyncResponse Entity:

@XmlRootElement 
public class AccountSyncResponse { 
    private String Result; 
    private String Value; 
    public AccountSyncResponse() {} 
    public String getResult() {return Result;} 
    public void setResult(String Result) {this.Result = Result;} 
    public String getValue() {return Value;} 
    public void setValue(String Value) {this.Value = Value;} 
}

REST Endpoint:

@POST 
@Consumes(MediaType.APPLICATION_JSON) 
@Produces(MediaType.APPLICATION_JSON) 
public AccountSyncResponse excute(AccountSyncRequest ASReq) { 
    AccountSyncResponse ASRes = new AccountSyncResponse(); 
    return ASRes; 
}

Currently, the returned JSON uses lowercase-first field names: {"result":"Create","value":"123456"}, but I need the first letter of each field name to be uppercase, like {"Result":"Create","Value":"123456"}. How can I control the format of the generated JSON field names?

Solutions #

Depending on which JSON serializer your JAX-RS implementation uses (most commonly Jackson or MOXy), here are the most straightforward approaches:

1. Use Jackson's @JsonProperty Annotation

If your project uses Jackson as the JSON processor (the default for many JAX-RS implementations like Jersey 2.x with Jackson support), you can explicitly specify the desired field name using the @JsonProperty annotation on either the field itself or its getter method:

Option 1: Annotate Getter Methods

@XmlRootElement 
public class AccountSyncResponse { 
    private String Result; 
    private String Value; 

    public AccountSyncResponse() {} 

    @JsonProperty("Result")
    public String getResult() {return Result;} 

    public void setResult(String Result) {this.Result = Result;} 

    @JsonProperty("Value")
    public String getValue() {return Value;} 

    public void setValue(String Value) {this.Value = Value;} 
}

Option 2: Annotate Fields Directly

@XmlRootElement 
public class AccountSyncResponse { 
    @JsonProperty("Result")
    private String Result; 
    @JsonProperty("Value")
    private String Value; 

    public AccountSyncResponse() {} 

    // Getter and setter methods remain unchanged
    public String getResult() {return Result;} 
    public void setResult(String Result) {this.Result = Result;} 
    public String getValue() {return Value;} 
    public void setValue(String Value) {this.Value = Value;} 
}

2. Use JAXB's @XmlElement Annotation

If your JAX-RS implementation uses MOXy (the default JSON processor for some Jersey versions or EE environments) and you're already using JAXB annotations like @XmlRootElement, you can use @XmlElement to define the JSON field name:

@XmlRootElement 
public class AccountSyncResponse { 
    private String Result; 
    private String Value; 

    public AccountSyncResponse() {} 

    @XmlElement(name = "Result")
    public String getResult() {return Result;} 

    public void setResult(String Result) {this.Result = Result;} 

    @XmlElement(name = "Value")
    public String getValue() {return Value;} 

    public void setValue(String Value) {this.Value = Value;} 
}

MOXy will respect the name attribute in @XmlElement when serializing to JSON, ensuring the field names use uppercase first letters.

3. Global Configuration (Avoid Per-Field Annotations)

If you want to apply the uppercase-first rule to all entities without annotating each field, you can configure the JSON serializer globally:

For Jackson:
Create a custom ObjectMapper with the UPPER_CAMEL_CASE naming strategy, then register it with your JAX-RS provider:

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.UPPER_CAMEL_CASE);

// Register with Jersey (example)
JacksonJaxbJsonProvider provider = new JacksonJaxbJsonProvider();
provider.setMapper(objectMapper);

This will automatically convert all field names to uppercase-first format for every serialized entity.

内容的提问来源于stack exchange，提问作者asabd