spring 22 对象绑定与类型转换

底层第一套转换接口与实现

classDiagram Formatter --|> Printer Formatter --|> Parser class Converters { Set~GenericConverter~ } class Converter class ConversionService class FormattingConversionService ConversionService <|-- FormattingConversionService FormattingConversionService o-- Converters Printer --> Adapter1 Adapter1 --> Converters Parser --> Adapter2 Adapter2 --> Converters Converter --> Adapter3 Adapter3 --> Converters <<interface>> Formatter <<interface>> Printer <<interface>> Parser <<interface>> Converter <<interface>> ConversionService

Printer 把其它类型转为 String
Parser 把 String 转为其它类型
Formatter 综合 Printer 与 Parser 功能
Converter 把类型 S 转为类型 T
Printer、Parser、Converter 经过适配转换成 GenericConverter 放入 Converters 集合
FormattingConversionService 利用其它们实现转换

底层第二套转换接口

classDiagram PropertyEditorRegistry o-- "多" PropertyEditor <<interface>> PropertyEditorRegistry <<interface>> PropertyEditor

PropertyEditor 把 String 与其它类型相互转换
PropertyEditorRegistry 可以注册多个 PropertyEditor 对象
与第一套接口直接可以通过 FormatterPropertyEditorAdapter 来进行适配

高层接口与实现

classDiagram TypeConverter <|-- SimpleTypeConverter TypeConverter <|-- BeanWrapperImpl TypeConverter <|-- DirectFieldAccessor TypeConverter <|-- ServletRequestDataBinder SimpleTypeConverter --> TypeConverterDelegate BeanWrapperImpl --> TypeConverterDelegate DirectFieldAccessor --> TypeConverterDelegate ServletRequestDataBinder --> TypeConverterDelegate TypeConverterDelegate --> ConversionService TypeConverterDelegate --> PropertyEditorRegistry <<interface>> TypeConverter <<interface>> ConversionService <<interface>> PropertyEditorRegistry

它们都实现了 TypeConverter 这个高层转换接口，在转换时，会用到 TypeConverter Delegate 委派ConversionService 与 PropertyEditorRegistry 真正执行转换（Facade 门面模式）
- 首先看是否有自定义转换器, @InitBinder 添加的即属于这种 (用了适配器模式把 Formatter 转为需要的 PropertyEditor)
- 再看有没有 ConversionService 转换
- 再利用默认的 PropertyEditor 转换
- 最后有一些特殊处理
SimpleTypeConverter 仅做类型转换
BeanWrapperImpl 为 bean 的属性赋值，当需要时做类型转换，走 Property
DirectFieldAccessor 为 bean 的属性赋值，当需要时做类型转换，走 Field
DataBinder 普通环境下的属性数据绑定类型转换
ServletRequestDataBinder 为 bean 的属性执行绑定，当需要时做类型转换，根据 directFieldAccess 选择走 Property 还是 Field，具备校验与获取校验结果功能

类型转换与数据绑定

点击查看代码

 //仅有类型转换功能
        SimpleTypeConverter converter = new SimpleTypeConverter();
        System.out.println(converter.convertIfNecessary("11", int.class));
        System.out.println(converter.convertIfNecessary("2011/01/02", Date.class));

//类型转换与数据绑定 ,根据反射，用 set 方法为 bean 属性赋值
        BeanWrapperImpl beanWrapper = new BeanWrapperImpl();
        S22Bean1 s22Bean1 = new S22Bean1();
        beanWrapper.setBeanInstance(s22Bean1);
        beanWrapper.setPropertyValue("name",13);
        beanWrapper.setPropertyValue("age","32");
        beanWrapper.setPropertyValue("date","2011/11/20");
        System.out.println(s22Bean1);

//类型转换与数据绑定， 利用反射，直接赋值给 bean 的属性，不需要 set 方法
        S22Bean2 s22Bean2 = new S22Bean2();
        DirectFieldAccessor fieldAccessor = new DirectFieldAccessor(s22Bean2);
        fieldAccessor.setPropertyValue("name",22);
        fieldAccessor.setPropertyValue("age","19");
        System.out.println(s22Bean2);

 //类型转换与数据绑定，根据 DirectFieldAccess 存不存在判断用哪种方法数据绑定  默认用 set 方法
        S22Bean2 s22Bean2 = new S22Bean2();
        DataBinder dataBinder = new DataBinder(s22Bean2);
        dataBinder.initDirectFieldAccess();
        MutablePropertyValues propertyValues = new MutablePropertyValues();
        propertyValues.add("name", 34);
        propertyValues.add("age", "12");
        dataBinder.bind(propertyValues);
        System.out.println(s22Bean2);

//类型转换与数据绑定，根据 DirectFieldAccess 存不存在判断用哪种方法数据绑定  默认用 set 方法
        S22Bean2 s22Bean2 = new S22Bean2();
        DataBinder dataBinder = new ServletRequestDataBinder(s22Bean2);
        //可直接对属性进行绑定
        dataBinder.initDirectFieldAccess();
        MockHttpServletRequest request = new MockHttpServletRequest();
        request.setParameter("name","13");
        request.setParameter("age","13");
        request.setParameter("date","2011/2/2");
        ServletRequestParameterPropertyValues propertyValues = new ServletRequestParameterPropertyValues(request);
        //也可以使用此方式进行数据绑定类型转换
//        propertyValues.add("name", 34);
//        propertyValues.add("age", "12");
        dataBinder.bind(propertyValues);
        System.out.println(s22Bean2);

基本的类型转换与数据绑定用法

SimpleTypeConverter
BeanWrapperImpl
DirectFieldAccessor
ServletRequestDataBinder

数据绑定工厂

点击查看代码

 public static void main(String[] args) throws Exception {
        MockHttpServletRequest request = new MockHttpServletRequest();
        request.setParameter("birthday", "1999|01|02");
        request.setParameter("address.name", "西安");

        User target = new User();
//         "1. 用工厂, 无转换功能"
//        ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(null, null);


//         "2. 用 @InitBinder 转换"          PropertyEditorRegistry PropertyEditor
//        InvocableHandlerMethod method = new InvocableHandlerMethod(new MyController(),
//                MyController.class.getMethod("aaa", WebDataBinder.class));
//        ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(List.of(method), null);

//         "3. 用 ConversionService 转换"    ConversionService Formatter
//        FormattingConversionService service = new FormattingConversionService();
//        service.addFormatter(new MyDateFormatter("用 ConversionService 方式扩展转换功能"));
//        ConfigurableWebBindingInitializer initializer = new ConfigurableWebBindingInitializer();
//        initializer.setConversionService(service);
//        ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(null, initializer);

//         "4. 同时加了 @InitBinder 和 ConversionService"
//        InvocableHandlerMethod method = new InvocableHandlerMethod(new MyController(),
//                MyController.class.getMethod("aaa", WebDataBinder.class));
//
//        FormattingConversionService service = new FormattingConversionService();
//        service.addFormatter(new MyDateFormatter("用 ConversionService 方式扩展转换功能"));
//        ConfigurableWebBindingInitializer initializer = new ConfigurableWebBindingInitializer();
//        initializer.setConversionService(service);
//        ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(List.of(method), initializer);

//         "5. 使用默认 ConversionService 转换"
        ApplicationConversionService service = new ApplicationConversionService();
        ConfigurableWebBindingInitializer initializer = new ConfigurableWebBindingInitializer();
        initializer.setConversionService(service);

        ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(null, initializer);

        WebDataBinder dataBinder = factory.createBinder(new ServletWebRequest(request), target, "user");
        dataBinder.bind(new ServletRequestParameterPropertyValues(request));
        System.out.println(target);
    }

    static class MyController {
        @InitBinder
        public void aaa(WebDataBinder dataBinder) {
            // 扩展 dataBinder 的转换器
            dataBinder.addCustomFormatter(new MyDateFormatter("用 @InitBinder 方式扩展的"));
        }
    }

    public static class User {
        @DateTimeFormat(pattern = "yyyy|MM|dd")
        private Date birthday;
        private Address address;

        public Address getAddress() {
            return address;
        }

        public void setAddress(Address address) {
            this.address = address;
        }

        public Date getBirthday() {
            return birthday;
        }

        public void setBirthday(Date birthday) {
            this.birthday = birthday;
        }

        @Override
        public String toString() {
            return "User{" +
                   "birthday=" + birthday +
                   ", address=" + address +
                   '}';
        }
    }

    public static class Address {
        private String name;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return "Address{" +
                   "name='" + name + '\'' +
                   '}';
        }
    }
}

ServletRequestDataBinderFactory 的用法和扩展点

可以解析控制器的 @InitBinder 标注方法作为扩展点，添加自定义转换器
- 控制器私有范围
可以通过 ConfigurableWebBindingInitializer 配置 ConversionService 作为扩展点，添加自定义转换器
- 公共范围
同时加了 @InitBinder 和 ConversionService 的转换优先级
1. 优先采用 @InitBinder 的转换器
2. 其次使用 ConversionService 的转换器
3. 使用默认转换器
4. 特殊处理（例如有参构造）

获取泛型参数

点击查看代码

 // 小技巧
        // 1. java api
        System.out.println(">>>>>>>>>>>>>>>>>>>>>>>");
        Type type = TeacherDao.class.getGenericSuperclass();
        System.out.println(type);

        if (type instanceof ParameterizedType parameterizedType) {
            System.out.println(parameterizedType.getActualTypeArguments()[0]);
        }

        // 2. spring api 1
        System.out.println(">>>>>>>>>>>>>>>>>>>>>>>");
        Class<?> t = GenericTypeResolver.resolveTypeArgument(TeacherDao.class, BaseDao.class);
        System.out.println(t);

        // 3. spring api 2
        System.out.println(">>>>>>>>>>>>>>>>>>>>>>>");
        System.out.println(ResolvableType.forClass(TeacherDao.class).getSuperType().getGeneric().resolve());

1. java api 获取泛型参数 2. spring api 获取泛型参数

posted @ 2022-07-02 16:22 xy7112 阅读(100) 评论(0) 收藏举报

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spring 22 对象绑定与类型转换

底层第一套转换接口与实现

底层第二套转换接口

高层接口与实现

类型转换与数据绑定

数据绑定工厂

获取泛型参数

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