类型转换与数据绑定【Spring源码学习】

simpleTypeConverter

类型转换

SimpleTypeConverter typeConverter = new SimpleTypeConverter();
Integer number = typeConverter.convertIfNecessary("13",int.class);
System.out.println(number);

BeanWrapper

通过反射原理为bean赋值，走的是set方法；

DataBinder

数据绑定器

public static void main(String[] args) {
    MyBean target = new MyBean();
    DataBinder dataBinder = new DataBinder(target);
    MutablePropertyValues pvs = new MutablePropertyValues();
    pvs.add("a","10");
    pvs.add("b","hello");
    dataBinder.bind(pvs);
    System.out.println(target);
}

static class MyBean{
    private int a;

    private String b;

    public int getA() {
        return a;
    }

    public void setA(int a) {
        this.a = a;
    }

    public String getB() {
        return b;
    }

    public void setB(String b) {
        this.b = b;
    }

    @Override
    public String toString() {
        return "MyBean{" +
                "a=" + a +
                ", b='" + b + '\'' +
                '}';
    }
}

DataBinder的扩展

可以通过ServletRequestDataBinderFactory 来对databinder进行扩展；

ConversionService

DefaultFormattingConversionService

// 默认conversionService
DefaultFormattingConversionService service = new DefaultFormattingConversionService();
ConfigurableWebBindingInitializer initializer = new ConfigurableWebBindingInitializer();
initializer.setConversionService(service);

// 用工厂创建DataBinder
ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(null,initializer);

WebDataBinder dataBinder = factory.createBinder(new ServletWebRequest(request), target, "user");

dataBinder.bind(new ServletRequestParameterPropertyValues(request));

绑定数据到指定的bean中时，如果是日期类型需要结合一个注解
代表当接收到了requet中参数类型是 yyyy|MM|dd时进行转换绑定到对应的属性上

@DateTimeFormat(pattern = "yyyy|MM|dd")
private Date a;

@InitBinder()

initBinder()也可以进行扩展；

优先采用initBinder的方法，再去找conversionService方法。