内省—beanutils工具包

Apache组织开发了一套用于操作JavaBean的API，这套API考虑到了很多实际开发中的应用场景，因此在实际开发中很多程序员使用这套API操作JavaBean，以简化程序代码的编写。

BeanUtils的作用：

1）支持String到8种基本数据类型的转换；

2）其他引用数据类型都需要注册转换器：ConvertUtils.register(Converter,Class);

public class Person {
    private String name;
    private String password;
    private Integer age;
    private Date birthday;
    getter/setter
}

采用beanutils设置属性

@Test
public void test1() throws Exception {
    Person person = new Person();
    BeanUtils.setProperty(person, "name", "zhangsan");
    System.out.println(person.getName());
}

采用beanutils拷贝对象的属性(基本类型)

@Test
public void test2() throws Exception {
    String name = "zhangsan";
    String password = "123";
    String age = "34";

    Person person = new Person();
    BeanUtils.setProperty(person, "name", name);
    BeanUtils.setProperty(person, "password", password);
    BeanUtils.setProperty(person, "age", age);// 自动类型转换，只支持8种基本数据类型

    System.out.println(person);
}

采用beanutils拷贝对象的属性(非基本类型)

@Test
public void test3() throws Exception {
    String name = "zhangsan";
    String password = "123";
    String age = "34";
    String birthday = "1980-09-05";

    Person person = new Person();
    BeanUtils.setProperty(person, "name", name);
    BeanUtils.setProperty(person, "password", password);
    BeanUtils.setProperty(person, "age", age);// 自动类型转换
    BeanUtils.setProperty(person, "birthday", birthday); // 类型转换失败
    System.out.println(person);
}

为让Date能够赋值到birthday属性上，我们给beanutils注册一个日期转换器。

改进代码如下：

@Test
public void test4() throws Exception {
    String name = "zhangsan";
    String password = "123";
    String age = "34";
    String birthday = "1980-09-05";

    ConvertUtils.register(new Converter() {
        @Override
        public Object convert(Class type, Object value) {
            if (value == null) {
                return null;
            }

            if (!(value instanceof String)) {
                throw new ConversionException("只支持String类型的转换!");
            }

            String str = (String) value;
            if (null == str || "".equals(str.trim())) {
                return null;
            }

            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            try {
                return format.parse(str);
            } catch (ParseException e) {
                throw new ConversionException(e);
            }
        }

    }, Date.class);

    Person person = new Person();
    BeanUtils.setProperty(person, "name", name);
    BeanUtils.setProperty(person, "password", password);
    BeanUtils.setProperty(person, "age", age);// 自动类型转换
    BeanUtils.setProperty(person, "birthday", birthday);
    System.out.println(person);
}

采用beanutils自带的日期类型转换器

@Test
public void test5() throws Exception {
    String name = "zhangsan";
    String password = "123";
    String age = "34";
    String birthday = "1980-09-05";

    ConvertUtils.register(new DateLocaleConverter(), Date.class);

    Person person = new Person();
    BeanUtils.setProperty(person, "name", name);
    BeanUtils.setProperty(person, "password", password);
    BeanUtils.setProperty(person, "age", age);// 自动类型转换
    BeanUtils.setProperty(person, "birthday", birthday);
    System.out.println(person);
}

收集数据到map中，并通过beanutils拷贝到指定的对象中去

@Test
public void test6() throws Exception {

    Person person = new Person();

    ConvertUtils.register(new DateLocaleConverter(), Date.class);

    Map<String, Object> map = new HashMap<String, Object>();
    map.put("name", "aa");
    map.put("password", "123");
    map.put("age", 23);
    map.put("birthday", "1980-09-05");

    // 用map集合中的值，填充bean的属性，
    // 注意：属性名称必须要一致
    BeanUtils.populate(person, map);

    System.out.println(person);
}