Java对象与Map间相互转换

将Java对象转为一个Map，以及将map转为对应Java对象，代码如下：

public class BeanMapUtil {

    private static ConcurrentHashMap<String, Map<String, String>> beanFieldCache = new ConcurrentHashMap<>();

    public static Map<String, String> toMap(Object bean) {
        if (bean == null) {
            return null;
        }
        Map<String, String> map = Maps.newHashMap();
        Map<String, String> beanFieldMap = getBeanFields(bean);
        try {
            for (Map.Entry<String, String> fieldEntry : beanFieldMap.entrySet()) {
                String fieldName = fieldEntry.getKey();
                String mapKey = fieldEntry.getValue();
                map.put(mapKey, BeanUtils.getProperty(bean, fieldName));
            }
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }
        return map;
    }

    public static void toBean(Map<String, String> map, Object result) {
        if (map.isEmpty()) {
            return;
        }
        try {
            for (Map.Entry<String, String> entry : map.entrySet()) {
                String key = entry.getKey();
                String value = entry.getValue();
                BeanUtils.setProperty(result, toBeanFieldName(key), value);
            }
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    private static Map<String, String> getBeanFields(Object bean) {
        if (bean == null) {
            return null;
        }
        if (beanFieldCache.contains(bean.getClass().getName())) {
            return beanFieldCache.get(bean.getClass().getName());
        }
        Map<String, String> map = Maps.newHashMap();
        for (Class clazz = bean.getClass(); clazz != Object.class; clazz = clazz.getSuperclass()) {
            Field[] fields = clazz.getDeclaredFields();
            for (Field field : fields) {
                String fieldName = field.getName();
                map.put(fieldName, toMapKey(fieldName));
            }
        }
        beanFieldCache.put(bean.getClass().getName(), map);
        return map;
    }

    private static String toMapKey(String fieldName) {
        if (fieldName == null) {
            return null;
        }
        StringBuilder underLineName = new StringBuilder();
        for (int i = 0; i < fieldName.length(); i++) {
            char c = fieldName.charAt(i);
            if (Character.isUpperCase(c)) {
                underLineName.append("_");
            }
            underLineName.append(upperCaseToLowerCase(c));
        }
        return underLineName.toString();
    }

    private static char upperCaseToLowerCase(char c) {
        if (c >= 'A' && c <= 'Z') {
            c += 32;
        }
        return c;
    }

    private static String toBeanFieldName(String key) {
        if (key == null) {
            return null;
        }
        StringBuilder camelFieldName = new StringBuilder();
        for (int i = 0; i < key.length(); i++) {
            char c = key.charAt(i);
            if (c == '_' && i + 1 < key.length()) {
                camelFieldName.append(lowerCaseToUpperCase(key.charAt(++i)));
            } else {
                camelFieldName.append(c);
            }
        }
        return camelFieldName.toString();
    }

    private static char lowerCaseToUpperCase(char c) {
        if (c >= 'a' && c <= 'z') {
            c -= 32;
        }
        return c;
    }

}

测试代码：

public class Parent {

    private String parentField;

    public String getParentField() {
        return parentField;
    }

    public void setParentField(String parentField) {
        this.parentField = parentField;
    }
}

public class Child extends Parent {

    private String childFieldA;

    private String childFieldB;

    private String childFieldC;

    public String getChildFieldA() {
        return childFieldA;
    }

    public void setChildFieldA(String childFieldA) {
        this.childFieldA = childFieldA;
    }

    public String getChildFieldB() {
        return childFieldB;
    }

    public void setChildFieldB(String childFieldB) {
        this.childFieldB = childFieldB;
    }

    public String getChildFieldC() {
        return childFieldC;
    }

    public void setChildFieldC(String childFieldC) {
        this.childFieldC = childFieldC;
    }
}

public class BeanMapTest {

    public static void main(String[] args) {
        Child child = new Child();
        child.setParentField("p1");
        child.setChildFieldA("c1");
        child.setChildFieldB("c2");
        child.setChildFieldC("c3");
        Map<String, String> map = BeanMapUtil.toMap(child);
        System.out.println(map);

        Child result = new Child();
        BeanMapUtil.toBean(map, result);
        System.out.println(JSON.toJSONString(result));
    }

}

运行结果：

{parent_field=p1, child_field_a=c1, child_field_c=c3, child_field_b=c2}
{"childFieldA":"c1","childFieldB":"c2","childFieldC":"c3","parentField":"p1"}