文章链接:tuacy

commons-beanutils是Apache提供的一个用于操作JAVA bean的工具包。里面提供了各种各样的工具类，让我们可以很方便的对bean对象的属性进行各种操作。

一 commons-beanutils依赖

pom方式的引入(maven项目)。

        <!-- https://mvnrepository.com/artifact/commons-beanutils/commons-beanutils -->
        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.9.4</version>
        </dependency>

二 commons-beanutils的使用

   关于commons-beanutils的使用主要是熟悉commons-beanutils库里面MethodUtils、ConstructorUtils、PropertyUtils、BeanUtils、ConvertUtils的使用。

2.1 MethodUtils

   MethodUtils通过反射对对象的方法做各种各样的操作。

   MethodUtils提供的一些静态方法：

   因为MethodUtils里面的方法都比较简单，所以我们就不给出例子了。

2.2 ConstructorUtils

   ConstructorUtils通过反射对对象的构造方法做各种操作。

   ConstructorUtils提供的静态方法：

   因为ConstructorUtils里面的方法都比较简单，所以我们就不给出例子了。

2.3 PropertyUtils

   PropertyUtils通过反射对对象的属性做各种操作。

   PropertyUtils提供的静态方法：

   PropertyUtils的使用，如下实例。

public class PropertyUtilsTest {

    public static class Address {
        private String email;

        public Address(String email) {
            this.email = email;
        }

        public String getEmail() {
            return email;
        }

        public void setEmail(String email) {
            this.email = email;
        }
    }

    public static class UserInfo {
        private String userName;
        private int age;
        private Address address;
        private List<String> friendsNames;
        private Map<String, String> tag;

        UserInfo(String userName, int age, Address address, List<String> friendsNames, Map<String, String> tag) {
            this.userName = userName;
            this.age = age;
            this.address = address;
            this.friendsNames = friendsNames;
            this.tag = tag;
        }

        public String getUserName() {
            return userName;
        }

        public void setUserName(String userName) {
            this.userName = userName;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public List<String> getFriendsNames() {
            return friendsNames;
        }

        public void setFriendsNames(List<String> friendsNames) {
            this.friendsNames = friendsNames;
        }

        public Map<String, String> getTag() {
            return tag;
        }

        public void setTag(Map<String, String> tag) {
            this.tag = tag;
        }

        public Address getAddress() {
            return address;
        }

        public void setAddress(Address address) {
            this.address = address;
        }
    }

    @Test
    public void test() {
        List<String> friendList = Lists.newArrayList("张三", "李四");
        Map<String, String> tag = Maps.newHashMap();
        tag.put("key1", "value1");
        tag.put("key2", "value2");
        UserInfo userInfo = new UserInfo("tuacy", 18, new Address("1@qq.com"), friendList, tag);
        try {
            Map<String, Object> propertyMap = PropertyUtils.describe(userInfo);
            Object friend0 = PropertyUtils.getIndexedProperty(userInfo, "friendsNames[0]"); // 张三
            Object friend0Temp = PropertyUtils.getIndexedProperty(userInfo, "friendsNames", 0); // 张三
            Object mapperProperty = PropertyUtils.getMappedProperty(userInfo, "tag(key1)"); // value1
            Object mapperPropertyTemp = PropertyUtils.getMappedProperty(userInfo, "tag", "key1"); // value1
            Object nestedProperty = PropertyUtils.getNestedProperty(userInfo, "address.email"); // 1@qq.com
            Object name = PropertyUtils.getProperty(userInfo, "userName"); // tuacy
            PropertyDescriptor propertyDescriptor = PropertyUtils.getPropertyDescriptor(userInfo, "userName"); // PropertyDescriptor是对属性的一个封装
            PropertyDescriptor[] propertyDescriptors = PropertyUtils.getPropertyDescriptors(userInfo); // 获取所有的属性
            Class<?> classType = PropertyUtils.getPropertyType(userInfo, "address"); // 获取属性的类型Address
            Method getMethod = PropertyUtils.getReadMethod(PropertyUtils.getPropertyDescriptor(userInfo, "userName")); // getUserName()方法
            Object simpleProperty = PropertyUtils.getSimpleProperty(userInfo, "userName");
            Method setMethod = PropertyUtils.getWriteMethod(PropertyUtils.getPropertyDescriptor(userInfo, "userName")); // setUserName()方法
            boolean isReadable = PropertyUtils.isReadable(userInfo, "userName"); // true
            boolean isWriteable = PropertyUtils.isWriteable(userInfo, "userName"); // true
            PropertyUtils.setIndexedProperty(userInfo, "friendsNames[0]", "张三第一次修改"); // 修改friendsNames第一个元素
            PropertyUtils.setIndexedProperty(userInfo, "friendsNames", 0, "张三第二次修改"); // 修改friendsNames第一个元素
            PropertyUtils.setMappedProperty(userInfo, "tag(key1)", "value1第一次修改"); // 修改tag key为key1的值
            PropertyUtils.setMappedProperty(userInfo, "tag", "key1", "value1第二次修改"); // 修改tag key为key1的值
            PropertyUtils.setNestedProperty(userInfo, "address.email", "1007@qq.com"); // 修改address属性对象对应的email属性
            PropertyUtils.setProperty(userInfo, "userName", "tuacy0"); // 修改userName对应的属性值
            PropertyUtils.setSimpleProperty(userInfo, "age", 19); // 修改age对应的属性值
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

2.4 BeanUtils

   BeanUtils通过反射提供了Bean对象的一些便捷操作方法。

   BeanUtils提供的静态方法：

   BeanUtils的使用：

public class BeanUtilsTest {

    public static class Address {
        private String email;

        public Address(String email) {
            this.email = email;
        }

        public String getEmail() {
            return email;
        }

        public void setEmail(String email) {
            this.email = email;
        }
    }

    public static class UserInfo {
        private String userName;
        private int age;
        private Address address;
        private List<String> friendsNames;
        private Map<String, String> tag;

        public UserInfo() {

        }

        public UserInfo(String userName, int age, Address address, List<String> friendsNames, Map<String, String> tag) {
            this.userName = userName;
            this.age = age;
            this.address = address;
            this.friendsNames = friendsNames;
            this.tag = tag;
        }

        public String getUserName() {
            return userName;
        }

        public void setUserName(String userName) {
            this.userName = userName;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public List<String> getFriendsNames() {
            return friendsNames;
        }

        public void setFriendsNames(List<String> friendsNames) {
            this.friendsNames = friendsNames;
        }

        public Map<String, String> getTag() {
            return tag;
        }

        public void setTag(Map<String, String> tag) {
            this.tag = tag;
        }

        public Address getAddress() {
            return address;
        }

        public void setAddress(Address address) {
            this.address = address;
        }
    }

    @Test
    public void test() {
        List<String> friendList = Lists.newArrayList("张三", "李四");
        Map<String, String> tag = Maps.newHashMap();
        tag.put("key1", "value1");
        tag.put("key2", "value2");
        UserInfo userInfo = new UserInfo("tuacy", 18, new Address("1@qq.com"), friendList, tag);
        try {
            Object voClone = BeanUtils.cloneBean(userInfo);
            UserInfo userInfo1 = new UserInfo();
            BeanUtils.copyProperties(userInfo1, userInfo);
            BeanUtils.copyProperty(userInfo1, "userName", "user1");
            Map<String, String> map = BeanUtils.describe(userInfo); // 获取所有的属性名字和属性对应的值，注意这里值都会转换成String
            String[] arrays =  BeanUtils.getArrayProperty(userInfo, "friendsNames"); // friendsNames数组转换成数组
            Object item = BeanUtils.getIndexedProperty(userInfo, "friendsNames[0]"); // 张三
            Object itemItem = BeanUtils.getIndexedProperty(userInfo, "friendsNames", 0); // 张三
            Object value = BeanUtils.getMappedProperty(userInfo, "tag(key1)"); // value1
            Object valueValue = BeanUtils.getMappedProperty(userInfo, "tag", "key1"); // value1
            Object email = BeanUtils.getNestedProperty(userInfo, "address.email"); // 1@qq.com
            String userName = BeanUtils.getProperty(userInfo, "userName"); // tuacy
            String userName0 = BeanUtils.getSimpleProperty(userInfo, "userName"); // tuacy
            UserInfo userInfo2 = new UserInfo();
            BeanUtils.populate(userInfo2, PropertyUtils.describe(userInfo)); // map转换成对象
            BeanUtils.setProperty(userInfo2, "userName", "tuacy0"); // map转换成对象
            NullPointerException nullPointerException = new NullPointerException("情况一");
            NullPointerException nullPointerException1 = new NullPointerException("情况二");
            BeanUtils.initCause(nullPointerException, nullPointerException1); // map转换成对象
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

2.5 ConvertUtils

   ConvertUtils提供了数据类型相互转换的一些方法。

   ConvertUtils静态方法介绍：

   ConvertUtils的使用。

public class ConvertUtilsTest {

    @Test
    public void test() {
        try {
            // 注册一个Date转换器，把字符串转换为Date
            ConvertUtils.register(new Converter() {
                @Override
                public <T> T convert(Class<T> type, Object value) {
                    try {
                        return (T) new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse((String) value);
                    } catch (ParseException e) {
                        return null;
                    }
                }
            }, Date.class);
            System.out.println(ConvertUtils.convert("2019-10-28 15:30:00", Date.class));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

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作者：tuacy
链接：https://www.jianshu.com/p/27c0ea663d83
来源：简书
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