Java 如何优雅的拷贝对象属性

场景

在 Java 项目中，经常遇到需要在对象之间拷贝属性的问题。然而，除了直接使用 Getter/Stter 方法，我们还有其他的方法么？当然有，例如 Apache Common Lang3 的 BeanUtils，然而 BeanUtils 却无法完全满足吾辈的需求，所以吾辈便自己封装了一个，这里分享出来以供参考。

需要大量复制对象的属性 对象之间的属性名可能是不同的 对象之间的属性类型可能是不同的

目标

简单易用的 API

copy: 指定需要拷贝的源对象和目标对象 prop: 拷贝指定对象的字段 props: 拷贝指定对象的多个字段 exec: 执行真正的拷贝操作 from: 重新开始添加其他对象的属性 get: 返回当前的目标对象 config: 配置拷贝的一些策略

思路

定义门面类 BeanCopyUtil 用以暴露出一些 API 定义每个字段的操作类 BeanCopyField，保存对每个字段的操作 定义 BeanCopyConfig，用于配置拷贝属性的策略 定义 BeanCopyOperator 作为拷贝的真正实现

图解

实现

注：反射部分依赖于 joor, JDK1.8 请使用 joor-java-8

定义门面类 BeanCopyUtil 用以暴露出一些 API

/** * java bean 复制操作的工具类 * * @author rxliuli */public class BeanCopyUtil<F, T> { /** * 源对象 */ private final F from; /** * 目标对象 */ private final T to; /** * 拷贝的字段信息列表 */ private final List<BeanCopyField> copyFieldList = new LinkedList<>(); /** * 配置信息 */ private BeanCopyConfig config = new BeanCopyConfig(); private BeanCopyUtil(F from, T to) { this.from = from; this.to = to; } /** * 指定需要拷贝的源对象和目标对象 * * @param from 源对象 * @param to 目标对象 * @param <F> 源对象类型 * @param <T> 目标对象类型 * @return 一个 {@link BeanCopyUtil} 对象 */ public static <F, T> BeanCopyUtil<F, T> copy(F from, T to) { return new BeanCopyUtil<>(from, to); } /** * 拷贝指定对象的字段 * * @param fromField 源对象中的字段名 * @param toField 目标对象中的字段名 * @param converter 将源对象中字段转换为目标对象字段类型的转换器 * @return 返回 {@code this} */ public BeanCopyUtil<F, T> prop(String fromField, String toField, Function<? super Object, ? super Object> converter) { copyFieldList.add(new BeanCopyField(fromField, toField, converter)); return this; } /** * 拷贝指定对象的字段 * * @param fromField 源对象中的字段名 * @param toField 目标对象中的字段名 * @return 返回 {@code this} */ public BeanCopyUtil<F, T> prop(String fromField, String toField) { return prop(fromField, toField, null); } /** * 拷贝指定对象的字段 * * @param field 源对象中与目标对象中的字段名 * @param converter 将源对象中字段转换为目标对象字段类型的转换器 * @return 返回 {@code this} */ public BeanCopyUtil<F, T> prop(String field, Function<? super Object, ? super Object> converter) { return prop(field, field, converter); } /** * 拷贝指定对象的字段 * * @param field 源对象中与目标对象中的字段名 * @return 返回 {@code this} */ public BeanCopyUtil<F, T> prop(String field) { return prop(field, field, null); } /** * 拷贝指定对象的多个字段 * * @param fields 源对象中与目标对象中的多个字段名 * @return 返回 {@code this} */ public BeanCopyUtil<F, T> props(String... fields) { for (String field : fields) { prop(field); } return this; } /** * 执行真正的拷贝操作 * * @return 返回 {@code this} */ public BeanCopyUtil<F, T> exec() { new BeanCopyOperator<>(from, to, copyFieldList, config).copy(); return this; } /** * 重新开始添加其他对象的属性 * 用于在执行完 {@link #exec()} 之后还想复制其它对象的属性 * * @param from 源对象 * @param <R> 源对象类型 * @return 一个新的 {@link BeanCopyUtil} 对象 */ public <R> BeanCopyUtil<R, T> from(R from) { return new BeanCopyUtil<>(from, to); } /** * 返回当前的目标对象 * * @return 当前的目标对象 */ public T get() { return to; } /** * 配置拷贝的一些策略 * * @param config 拷贝配置对象 * @return 返回 {@code this} */ public BeanCopyUtil<F, T> config(BeanCopyConfig config) { this.config = config; return this; }}

定义每个字段的操作类 BeanCopyField，保存对每个字段的操作

/** * 拷贝属性的每一个字段的选项 * * @author rxliuli */public class BeanCopyField { private String from; private String to; private Function<? super Object, ? super Object> converter; public BeanCopyField() { } public BeanCopyField(String from, String to, Function<? super Object, ? super Object> converter) { this.from = from; this.to = to; this.converter = converter; } public String getFrom() { return from; } public BeanCopyField setFrom(String from) { this.from = from; return this; } public String getTo() { return to; } public BeanCopyField setTo(String to) { this.to = to; return this; } public Function<? super Object, ? super Object> getConverter() { return converter; } public BeanCopyField setConverter(Function<? super Object, ? super Object> converter) { this.converter = converter; return this; }}

定义 BeanCopyConfig，用于配置拷贝属性的策略

/** * 拷贝属性的配置 * * @author rxliuli */public class BeanCopyConfig { /** * 同名的字段自动复制 */ private boolean same = true; /** * 覆盖同名的字段 */ private boolean override = true; /** * 忽略 {@code null} 的源对象属性 */ private boolean ignoreNull = true; /** * 尝试进行自动转换 */ private boolean converter = true; public BeanCopyConfig() { } public BeanCopyConfig(boolean same, boolean override, boolean ignoreNull, boolean converter) { this.same = same; this.override = override; this.ignoreNull = ignoreNull; this.converter = converter; } public boolean isSame() { return same; } public BeanCopyConfig setSame(boolean same) { this.same = same; return this; } public boolean isOverride() { return override; } public BeanCopyConfig setOverride(boolean override) { this.override = override; return this; } public boolean isIgnoreNull() { return ignoreNull; } public BeanCopyConfig setIgnoreNull(boolean ignoreNull) { this.ignoreNull = ignoreNull; return this; } public boolean isConverter() { return converter; } public BeanCopyConfig setConverter(boolean converter) { this.converter = converter; return this; }}

定义 BeanCopyOperator 作为拷贝的真正实现

/** * 真正执行 copy 属性的类 * * @author rxliuli */public class BeanCopyOperator<F, T> { private static final Logger log = LoggerFactory.getLogger(BeanCopyUtil.class); private final F from; private final T to; private final BeanCopyConfig config; private List<BeanCopyField> copyFieldList; public BeanCopyOperator(F from, T to, List<BeanCopyField> copyFieldList, BeanCopyConfig config) { this.from = from; this.to = to; this.copyFieldList = copyFieldList; this.config = config; } public void copy() { //获取到两个对象所有的属性 final Map<String, Reflect> fromFields = Reflect.on(from).fields(); final Reflect to = Reflect.on(this.to); final Map<String, Reflect> toFields = to.fields(); //过滤出所有相同字段名的字段并进行拷贝 if (config.isSame()) { final Map<ListUtil.ListDiffState, List<String>> different = ListUtil.different(new ArrayList<>(fromFields.keySet()), new ArrayList<>(toFields.keySet())); copyFieldList = Stream.concat(different.get(ListUtil.ListDiffState.common).stream() .map(s -> new BeanCopyField(s, s, null)), copyFieldList.stream()) .collect(Collectors.toList()); } //根据拷贝字段列表进行拷贝 copyFieldList.stream()//忽略空值.filter(beanCopyField -> !config.isIgnoreNull() || fromFields.get(beanCopyField.getFrom()).get() != null)//覆盖属性.filter(beanCopyField -> config.isOverride() || toFields.get(beanCopyField.getTo()).get() == null)//如果没有转换器，则使用默认的转换器.peek(beanCopyField -> { if (beanCopyField.getConverter() == null) { beanCopyField.setConverter(Function.identity()); }}).forEach(beanCopyField -> { final String fromField = beanCopyField.getFrom(); final F from = fromFields.get(fromField).get(); final String toField = beanCopyField.getTo(); try { to.set(toField, beanCopyField.getConverter().apply(from)); } catch (ReflectException e) { log.warn('Copy field failed, from {} to {}, exception is {}', fromField, toField, e.getMessage()); }}); }}

使用

使用流程图

测试

代码写完了，让我们测试一下！

public class BeanCopyUtilTest { private final Logger log = LoggerFactory.getLogger(getClass()); private Student student; private Teacher teacher; @Before public void before() { student = new Student('琉璃', 10, '女', 4); teacher = new Teacher(); } @Test public void copy() { //简单的复制（类似于 BeanUtils.copyProperties） BeanCopyUtil.copy(student, teacher).exec(); log.info('teacher: {}', teacher); assertThat(teacher).extracting('age').containsOnlyOnce(student.getAge()); } @Test public void prop() { //不同名字的属性 BeanCopyUtil.copy(student, teacher).prop('sex', 'sex', sex -> Objects.equals(sex, '男')).prop('realname', 'name').exec(); assertThat(teacher).extracting('name', 'age', 'sex').containsOnlyOnce(student.getRealname(), student.getAge(), false); } @Test public void prop1() { //不存的属性 assertThat(BeanCopyUtil.copy(student, teacher).prop('sex', 'sex', sex -> Objects.equals(sex, '男')).prop('realname', 'name2').exec().get()).extracting('age', 'sex').containsOnlyOnce(student.getAge(), false); } @Test public void from() { final Teacher lingMeng = new Teacher().setName('灵梦').setAge(17); //测试 from 是否覆盖 assertThat(BeanCopyUtil.copy(student, teacher).prop('sex', 'sex', sex -> Objects.equals(sex, '男')).prop('realname', 'name').exec().from(lingMeng).exec().get()).extracting('name', 'age', 'sex').containsOnlyOnce(lingMeng.getName(), lingMeng.getAge(), false); } @Test public void get() { //测试 get 是否有效 assertThat(BeanCopyUtil.copy(student, teacher).prop('sex', 'sex', sex -> Objects.equals(sex, '男')).prop('realname', 'name').exec().get()).extracting('name', 'age', 'sex').containsOnlyOnce(student.getRealname(), student.getAge(), false); } @Test public void config() { //不自动复制同名属性 assertThat(BeanCopyUtil.copy(new Student().setAge(15), new Teacher()).config(new BeanCopyConfig().setSame(false)).exec().get()).extracting('age').containsOnlyNulls(); //不覆盖不为空的属性 assertThat(BeanCopyUtil.copy(new Student().setAge(15), new Teacher().setAge(10)).config(new BeanCopyConfig().setOverride(false)).exec().get()).extracting('age').containsOnlyOnce(10); //不忽略源对象不为空的属性 assertThat(BeanCopyUtil.copy(new Student(), student).config(new BeanCopyConfig().setIgnoreNull(false)).exec().get()).extracting('realname', 'age', 'sex', 'grade').containsOnlyNulls(); } /** * 测试学生类 */ private static class Student { /** * 姓名 */ private String realname; /** * 年龄 */ private Integer age; /** * 性别，男/女 */ private String sex; /** * 年级，1 - 6 */ private Integer grade; public Student() { } public Student(String realname, Integer age, String sex, Integer grade) { this.realname = realname; this.age = age; this.sex = sex; this.grade = grade; } public String getRealname() { return realname; } public Student setRealname(String realname) { this.realname = realname; return this; } public Integer getAge() { return age; } public Student setAge(Integer age) { this.age = age; return this; } public String getSex() { return sex; } public Student setSex(String sex) { this.sex = sex; return this; } public Integer getGrade() { return grade; } public Student setGrade(Integer grade) { this.grade = grade; return this; } @Override public String toString() { return ToStringBuilder.reflectionToString(this); } } /** * 测试教师类 */ private static class Teacher { /** * 姓名 */ private String name; /** * 年龄 */ private Integer age; /** * 性别，true 男，false 女 */ private Boolean sex; /** * 职位 */ private String post; public Teacher() { } public Teacher(String name, Integer age, Boolean sex, String post) { this.name = name; this.age = age; this.sex = sex; this.post = post; } public String getName() { return name; } public Teacher setName(String name) { this.name = name; return this; } public Integer getAge() { return age; } public Teacher setAge(Integer age) { this.age = age; return this; } public Boolean getSex() { return sex; } public Teacher setSex(Boolean sex) { this.sex = sex; return this; } public String getPost() { return post; } public Teacher setPost(String post) { this.post = post; return this; } @Override public String toString() { return ToStringBuilder.reflectionToString(this); } }}

如果没有发生什么意外，那么一切将能够正常运行！

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