Java注解

1. 定义注解

@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)@Documented@Inheritedpublic @interface Persistent {enum FilterType {Numeric, String};enum ResType {Rat, Cat, RatCat, None}short index() default 0;String id() default "";String value() default "";FilterType filterType() default FilterType.Numeric;boolean isVisible() default true;ResType resType() default ResType.None;}

2. 定义JavaBean

public class Tuple<T, V> implements ITuple<T, V> {private T key;private V value;@Overridepublic T getKey() {return key;}@Overridepublic void setKey(T key) {this.key = key;}@Overridepublic V getValue() {return value;}@Overridepublic void setValue(V value) {this.value = value;}}

public class Column<T, V> extends Tuple<T, V> implements IColumn<T, V> {private byte filterType;private boolean isVisible;@Overridepublic byte getFilterType() {return filterType;}@Overridepublic void setFilterType(byte filterType) {this.filterType = filterType;}@Overridepublic boolean isVisible() {return this.isVisible;}@Overridepublic void setVisible(boolean isVisible) {this.isVisible = isVisible;}}

public class Row<T, V, K extends ITuple<T, V>> implements IRow<T, V, K> {private List<K> columns;@Overridepublic List<K> getColumns() {return columns;}@Overridepublic void setColumns(List<K> columns) {this.columns = columns;}}

public class User implements IUser {@Persistent(index = 0, id = "name", filterType = FilterType.String)private String name;@Persistent(index = 3, id = "age", isVisible = false)private short age;@Persistent(index = 2)private byte gendar;public byte getGendar() {return gendar;}public void setGendar(byte gendar) {this.gendar = gendar;}public short getAge() {return age;}public void setAge(short age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}}

3. Demo

public class Main {public static void main(String[] args) {List<LoginUser> users = new ArrayList<LoginUser>();LoginUser user = new LoginUser();user.setAge((short) 26);user.setName("9528");user.setGendar((byte) 0);user.setLoginTime(new Date());users.add(user);user = new LoginUser();user.setAge((short) 27);user.setName("9527");user.setGendar((byte) 1);user.setLoginTime(new Date());users.add(user);WebUser webUser = getWebUser(users);List<? extends IColumn<String, String>> columns = webUser.getColumns();List<? extends IRow<String, String, ? extends ITuple<String, String>>> rows = webUser.getRows();for (IColumn<String, String> column : columns) {System.out.print(column.getKey());System.out.print(":");System.out.print(column.getValue());System.out.print("#");}System.out.println();for (IRow<String, String, ? extends ITuple<String, String>> row : rows) {List<? extends ITuple<String, String>> cols = row.getColumns();for (ITuple<String, String> col : cols) {System.out.print(col.getKey());System.out.print(":");System.out.print(col.getValue());System.out.print("#");}System.out.println();}System.out.println("---------");}private static WebUser getWebUser(List<LoginUser> users) {WebUser result = new WebUser();LoginUser first = users.get(0);List<Column<String, String>> columns = getColumns(first);result.setColumns(columns);List<Row<String, String, Tuple<String, String>>> rows = new ArrayList<Row<String, String, Tuple<String, String>>>();for (LoginUser user : users) {Row<String, String, Tuple<String, String>> row = new Row<String, String, Tuple<String, String>>();List<Tuple<String, String>> cols = getCols(user);row.setColumns(cols);rows.add(row);}result.setRows(rows);return result;}private static List<Field> getFields(Class<?> type) {List<Field> result = new ArrayList<Field>();for (Field field : type.getDeclaredFields()) {result.add(field);}if (type.getSuperclass().getDeclaredFields().length > 0) {result.addAll(getFields(type.getSuperclass()));}return result;}private static List<Tuple<String, String>> getCols(LoginUser user) {List<PersistentItem<String, String>> result = new ArrayList<PersistentItem<String, String>>();for (Field field : getFields(LoginUser.class)) {Persistent persistent = field.getAnnotation(Persistent.class);if (persistent != null) {PersistentItem<String, String> item = new PersistentItem<String, String>();item.setKey(getPersistentId(persistent, field));field.setAccessible(true);String value = null;try {value = String.valueOf(field.get(user));field.setAccessible(false);} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}item.setValue(value);item.setIndex(persistent.index());result.add(item);}}sortItems(result);return convert(result);}private static List<Column<String, String>> getColumns(LoginUser first) {List<PersistentItem<String, String>> result = new ArrayList<PersistentItem<String, String>>();for (Field field : getFields(LoginUser.class)) {Persistent persistent = field.getAnnotation(Persistent.class);if (persistent != null) {PersistentItem<String, String> item = new PersistentItem<String, String>();item.setFilterType((byte) persistent.filterType().ordinal());item.setKey(getPersistentId(persistent, field));item.setValue(getResValue(persistent.id()));item.setVisible(persistent.isVisible());item.setIndex(persistent.index());result.add(item);}}sortItems(result);return convert(result);}private static String getPersistentId(Persistent persistent, Field field) {String result = persistent.id();if (result == null || result.isEmpty()) {result = field.getName();}return result;}@SuppressWarnings("unchecked")private static <T extends Tuple<String, String>> List<T> convert(List<PersistentItem<String, String>> persistents) {return (List<T>) persistents;}private static void sortItems(List<PersistentItem<String, String>> result) {Collections.sort(result, new Comparator<PersistentItem<String, String>>() {@Overridepublic int compare(PersistentItem<String, String> arg0, PersistentItem<String, String> arg1) {return arg0.getIndex() - arg1.getIndex();}});}private static String getResValue(String id) {return id;}}