package com.shkj.web.core.config;

import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;

import java.util.Collection;
import java.util.List;

/**
 * <pre>
 * 此modifier主要做的事情为：
 * 1.当序列化类型为数组集合时，当值为null时，序列化成[]
 * 2.String类型值序列化为""
 * * @author lch
 * </pre>
 */
public class MyBeanSerializerModifier extends BeanSerializerModifier {

    @Override
    public List<BeanPropertyWriter> changeProperties(SerializationConfig config,
                                                     BeanDescription beanDesc,
                                                     List<BeanPropertyWriter> beanProperties) {
        // 循环所有的beanPropertyWriter
        for (int i = 0; i < beanProperties.size(); i++) {
            BeanPropertyWriter writer = beanProperties.get(i);
            // 判断字段的类型，如果是数组或集合则注册nullSerializer
            if (isArrayType(writer)) {
                // 给writer注册一个自己的nullSerializer
                writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullArrayJsonSerializer());
            } else
            if (isStringType(writer)) {
                writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullStringJsonSerializer());
            } else if (isNumberType(writer)) {
                writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullNumberJsonSerializer());
            } else if (isBooleanType(writer)) {
                writer.assignNullSerializer(new CustomizeNullJsonSerializer.NullBooleanJsonSerializer());
            }
        }
        return beanProperties;
    }

    /**
     * 是否是数组
     */
    private boolean isArrayType(BeanPropertyWriter writer) {
        Class<?> clazz = writer.getType().getRawClass();
        return clazz.isArray() || Collection.class.isAssignableFrom(clazz);
    }

    /**
     * 是否是String
     */
    private boolean isStringType(BeanPropertyWriter writer) {
        Class<?> clazz = writer.getType().getRawClass();
        return CharSequence.class.isAssignableFrom(clazz) || Character.class.isAssignableFrom(clazz);
    }

    /**
     * 是否是数值类型
     */
    private boolean isNumberType(BeanPropertyWriter writer) {
        Class<?> clazz = writer.getType().getRawClass();
        return Number.class.isAssignableFrom(clazz);
    }

    /**
     * 是否是boolean
     */
    private boolean isBooleanType(BeanPropertyWriter writer) {
        Class<?> clazz = writer.getType().getRawClass();
        return clazz.equals(Boolean.class);
    }

}

