使用 SnakeYaml 将 java 对象写入文件 - 使用 Yaml.dump() 时不会写出内部对象列表
Writing a java object to a file using SnakeYaml - List of inner objects are not writen out when using Yaml.dump()
我无法使用 SnakeYaml 将 java 对象写入 yml 文件。我设置了一个 spring 引导项目,其中包含一个简单的 application.yml,我将其转换为一组 java 对象。在实际应用程序中添加了一些对象,当应用程序完成后我想写出新的 application.yml.
输入 application.yml 如下所示:
sample:
name: toyota
cars:
- model: prius
colour: silver
- model: avensis
colour: red
映射这个application.yml的java对象:
@Configuration
@ConfigurationProperties(prefix="sample")
public class Config {
private String name;
private final List<Car> cars = new ArrayList<>();
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Car> getCars() {
return cars;
}
}
以及写出 yaml 的示例 class:
@Component
public class Example {
@Autowired
private Config config;
@PostConstruct
private void init(){
Yaml yaml = new Yaml();
StringWriter writer = new StringWriter();
yaml.dump(config, writer);
System.out.println(writer.toString());
}
}
输出只是:name: toyota
(省略了一些也被写出的 yaml 设置)。但是我希望输出与输入完全相同:
sample:
name: toyota
cars:
- model: prius
colour: silver
- model: avensis
colour: red
有办法吗?
编辑:
用户 flyx 正确指出了以下 documentation。
我调整后的代码:
Constructor constructor = new Constructor(Config.class);
TypeDescription configDescription = new TypeDescription(Config.class);
configDescription.putListPropertyType("cars", Car.class);
constructor.addTypeDescription(configDescription);
Yaml yaml = new Yaml(constructor);
StringWriter writer = new StringWriter();
yaml.dump(config, writer);
System.out.println(writer.toString());
给出以下输出:
$$beanFactory: !!org.springframework.beans.factory.support.DefaultListableBeanFactory
allowBeanDefinitionOverriding: true
allowEagerClassLoading: true
autowireCandidateResolver: !!org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver {}
beanClassLoader: !!sun.misc.Launcher$AppClassLoader {}
beanExpressionResolver: !!org.springframework.context.expression.StandardBeanExpressionResolver {}
cacheBeanMetadata: true
conversionService: null
dependencyComparator: !!org.springframework.core.annotation.AnnotationAwareOrderComparator {}
parentBeanFactory: null
serializationId: application
tempClassLoader: null
typeConverter: !!org.springframework.beans.SimpleTypeConverter {conversionService: null}
name: toyota
SnakeYAML 由于类型擦除,无法在运行时获取 List
的元素类型。该文档包含您需要执行的操作的 example。
像这样的东西应该可以工作:
@PostConstruct
private void init(){
Constructor c = new Constructor(Config.class);
TypeDescription configD = new TypeDescription(Config.class);
configD.putListPropertyType("cars", Car.class);
c.addTypeDescription(configD);
Yaml yaml = new Yaml(c);
StringWriter writer = new StringWriter();
yaml.dump(config, writer);
System.out.println(writer.toString());
}
如果 Car 列表中没有明确的 setter,则不会打印该列表。
更改后:
private final List<Car> cars = new ArrayList<>();
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Car> getCars() {
return cars;
}
为此:
private List<Car> cars = new ArrayList<>();
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public void setCars(List<Car> cars) {
this.cars = cars;
}
public List<Car> getCars() {
return cars;
}
代码有效。