我有一个名为“test”的表,其中包含 Postgres 9.3 中 json 类型的列“sample_column”。我正在尝试使用 Spring / JPA 将以下内容写入列中:{“name”:“更新的名称”}
我在其他帖子中读到,我需要添加自定义转换器以将字符串映射到 json 类型。这是我现在的代码:
TestDAO.java:
@Entity
@Table(name="test")
public class TestDAO implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id", unique=true, nullable=false)
private Long id;
@Column(name="sample_column")
@Convert(converter = MyCustomConverter.class)
private MyCustomClass sampleColumn;
// Getter / Setters
}
用于映射 json 内容的 CustomClass:
public class MyCustomClass {
@JsonProperty("name")
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
最后是 ConverterClass:
@javax.persistence.Converter
public class MyCustomConverter implements AttributeConverter<MyCustomClass, String> {
private final static ObjectMapper objectMapper = new ObjectMapper();
@Override
@NotNull
public String convertToDatabaseColumn(@NotNull MyCustomClass myCustomObject) {
try {
return objectMapper.writeValueAsString(myCustomObject);
} catch (Exception ex) {
return null;
}
}
@Override
@NotNull
public MyCustomClass convertToEntityAttribute(@NotNull String databaseDataAsJSONString) {
try {
return objectMapper.readValue(databaseDataAsJSONString, MyCustomClass.class);
} catch (Exception ex) {
return null;
}
}
}
现在,我尝试按如下方式设置 json 列:
testDAO.getSampleColumn().setName("Updated name");
testRepository.saveAndFlush(testDAO);
但是当我尝试保存它时,出现以下错误:
Caused by: org.postgresql.util.PSQLException: ERROR: column "sample_column" is of type json but expression is of type character varying
Hint: You will need to rewrite or cast the expression.
但是,我可以使用读取 JSON 列testDAO.getSampleColumn().getName();
这里有什么问题?我不想向表中添加任何转换以自动将 Varying 转换为 Json。
Thanks.