Apache BeanUtils工具介绍

迈不过友情╰ 2024-03-24 19:42 66阅读 0赞

beanutils，顾名思义，是java bean的一个工具类，可以帮助我们方便的读取(get)和设置(set)bean属性值、动态定义和访问bean属性；细心的话，会发现其实JDK已经提供了一个java.beans包，同样可以实现以上功能，只不过使用起来比较麻烦，所以诞生了apache commons beanutils；看源码就知道，其实apache commons beanutils就是基于jdk的java.beans包实现的。

maven：

<dependency>
            <groupId>commons-chain</groupId>
            <artifactId>commons-chain</artifactId>
            <version>1.2</version>
    </dependency>

commons-chain包主要有以下三个工具类：BeanUtils、PropertyUtils、ConvertUtils

#### 1、设置、访问Bean的属性 ####

##### 1.1）javabean一般有以下几个特性： #####

1）类必须是public访问权限，且需要有一个public的无参构造方法，之所以这样主要是方便利用Java的反射动态创建对象实例：

Class beanClass = Class.forName(className);

Object beanInstance = beanClass.newInstance();

2）由于javabean的构造方法是无参的，所以我们的bean的行为配置（即设置bean的属性值）不能在构造方法完成，必须通过set方法来设置属性值。这里的setter方法会按一定的约定来命名，如setHireDate、setName。。。

3）读取和设置bean属性值的命名约定，即getter方法和setter方法，不过这里需要特别注意boolean类型的约定，如下示例：

private String firstName;
    private String lastName;
    private Date hireDate;
    private boolean isManager;
    public String getFirstName();
    public void setFirstName(String firstName);
    public String getLastName();
    public void setLastName(String lastName);
    public Date getHireDate();
    public void setHireDate(Date hireDate);
    public boolean isManager();
    public void setManager(boolean manager);

4）并不是必须为每个属性提供setter和getter方法，我们可以只定义一个属性的getter方法而不定义setter方法，这样的属性一般是只读属性；

##### 1.2）实战 #####

可以通过BeanUtils和PropertyUtils设置、获取Bean的属性。

**1）PropertyUtils设置、获取属性：**

*  基本数据类型：
    
     *  PropertyUtils.getSimpleProperty(Object, String)
     *  PropertyUtils.setSimpleProperty(Object, String, Object)
 *  索引类型：
    
     *  PropertyUtils.getIndexedProperty(Object, String)

*   *  PropertyUtils.getIndexedProperty(Object, String, int)
     *  PropertyUtils.setIndexedProperty(Object, String, Object)
     *  PropertyUtils.setIndexedProperty(Object, String, int, Object)
 *  Map类型：
    
     *  PropertyUtils.getMappedProperty(Object, String)

*   *  PropertyUtils.getMappedProperty(Object, String, String)
     *  PropertyUtils.setMappedProperty(Object, String, Object)
     *  PropertyUtils.setMappedProperty(Object, String, String, Object)
 *  嵌套类型：
    
     *  PropertyUtils.getNestedProperty(Object, String)
     *  PropertyUtils.setNestedProperty(Object, String, Object)
 *  通用类型：
    
     *  PropertyUtils.getProperty(Object, String)
     *  PropertyUtils.setProperty(Object, String, Object)

**示例：**

//定义bean
    @Data
    @ToString
    public class Course {
    	private String name;
        private List<String> codes;
        private Map<String, Student> enrolledStudent = new HashMap<>();
    }
    @Data
    @ToString
    public class Student {
    	private String name;
    }
    
    //测试
    Course course = new Course(); //该类必须是public的、且有默认构造方法
    
    String name = "Computer Science";
    List<String> codes = Arrays.asList("CS", "CS01");
    
    //Simple Property
    PropertyUtils.setSimpleProperty(course, "name", name);
    PropertyUtils.setSimpleProperty(course, "codes", codes);
    System.out.println(course);
    String nameV = (String)PropertyUtils.getSimpleProperty(course, "name");
    System.out.println(nameV);
    
    //Indexed Property
    PropertyUtils.setIndexedProperty(course, "codes[1]", "CS02");
    PropertyUtils.setIndexedProperty(course, "codes", 1, "CS03");
    System.out.println(course);
    String indexedProperty = (String)PropertyUtils.getIndexedProperty(course, "codes", 1);
    String indexedProperty2 = (String)PropertyUtils.getIndexedProperty(course, "codes[1]");
    System.out.println(indexedProperty + "," + indexedProperty2);
    
    Student student = new Student();
    String studentName = "Joe";
    student.setName(studentName);
    
    //Mapped Property
    PropertyUtils.setMappedProperty(course, "enrolledStudent(ST-1)", student);
    PropertyUtils.setMappedProperty(course, "enrolledStudent", "ST-1", student);
    System.out.println(course);
    Student mappedProperty = (Student)PropertyUtils.getMappedProperty(course, "enrolledStudent", "ST-1");
    Student mappedProperty2 = (Student)PropertyUtils.getMappedProperty(course, "enrolledStudent(ST-1)");
    System.out.println(mappedProperty + "," + mappedProperty2);
    
    //Nested Property
    PropertyUtils.setNestedProperty(course, "enrolledStudent(ST-1).name", "Joe_1");
    String nameValue = (String) PropertyUtils.getNestedProperty(course, "enrolledStudent(ST-1).name");
    //等价于 String name = course.getEnrolledStudent("ST-1").getName();
    System.out.println(nameValue);

以上还可以使用下面的方式：

private static void test1_1() throws Exception {
            Course course = new Course();
            
            String name = "Computer Science";
            List<String> codes = Arrays.asList("CS", "CS01");
            
            //Simple Property
            PropertyUtils.setProperty(course, "name", name);
            PropertyUtils.setProperty(course, "codes", codes);
            System.out.println(course);
            String nameV = (String)PropertyUtils.getProperty(course, "name");
            System.out.println(nameV);
            
            //Indexed Property
            PropertyUtils.setProperty(course, "codes[1]", "CS02");
            System.out.println(course);
            
            Student student = new Student();
            String studentName = "Joe";
            student.setName(studentName);
            
            //Mapped Property
            PropertyUtils.setProperty(course, "enrolledStudent(ST-1)", student);
            System.out.println(course);
            
            //Nested Property
            PropertyUtils.setProperty(course, "enrolledStudent(ST-1).name", "Joe_1");
            String nameValue = (String) PropertyUtils.getProperty(course, "enrolledStudent(ST-1).name");
            System.out.println(nameValue);
    }

**2）BeanUtils设置、获取属性：**

BeanUtils只有以下两个方法来设置、获取属性

*  BeanUtils.getProperty(Object, String)
 *  BeanUtils.setProperty(Object, String, Object)

示例：

private static void test1_2() throws Exception {
            Course course = new Course();
            
            String name = "Computer Science";
            List<String> codes = Arrays.asList("CS", "CS01");
            
            //Simple Property
            BeanUtils.setProperty(course, "name", name);
            BeanUtils.setProperty(course, "codes", codes);
            System.out.println(course);
            String nameV = (String)BeanUtils.getProperty(course, "name");
            System.out.println(nameV);
            
            //Indexed Property
            BeanUtils.setProperty(course, "codes[1]", "CS02");
            System.out.println(course);
            
            Student student = new Student();
            String studentName = "Joe";
            student.setName(studentName);
            
            //Mapped Property
            BeanUtils.setProperty(course, "enrolledStudent(ST-1)", student);
            System.out.println(course);
            
            //Nested Property
            BeanUtils.setProperty(course, "enrolledStudent(ST-1).name", "Joe_1");
            String nameValue = (String) BeanUtils.getProperty(course, "enrolledStudent(ST-1).name");
            System.out.println(nameValue);
    }

#### 2、拷贝Bean的属性 ####

##### 2.1）BeanUtils有一下两个方法： #####

*  populate：把Map里的键值对值拷贝到bean的属性值中；
 *  copyProperties：拷贝一个bean的属性到另外一个bean中，注意是浅拷贝

注意：populate和copyProperties的区别，对于Integer、Float、Boolean类型前者（populate）对于null值，在拷贝到Bean的属性后会变成默认值。

**1）populate：**

//bean定义
    import java.util.Date;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    @Data
    @NoArgsConstructor
    public class Employee {
    	private Integer id;
    	private String name;
    	private Boolean isGood;
       private Float score;
    	private Date createTime;
    	
    	public Employee(Integer id, String name, Boolean isGood, Float score, Date createTime) {
               this.id = id;
               this.name = name;
               this.isGood = isGood;
               this.score = score;
               this.createTime = createTime;
    	}
    }
    //测试
    Map<String, Object> map = new HashMap<>(2);
    map.put("id", null);
    map.put("name", "employee1");
    map.put("isGood", null);
    map.put("createTime", new Date()); //如果是null，会报错
    map.put("add", "add1");
    // map > obj
    Employee e = new Employee();
    BeanUtils.populate(e, map);
    System.out.println(e); //Employee(id=0, name=employee1, isGood=false, createTime=Tue Aug 15 10:42:14 CST 2023)
    
    //支持类型转换
    Map<String, Object> map = new HashMap<>(5);
    map.put("id", "123"); 
    map.put("name", 1.9);
    map.put("isGood", "2"); 
    map.put("score", null);
    map.put("createTime", new Date());
    map.put("add", "add1");
    // map > obj
    Employee e = new Employee();
    BeanUtils.populate(e, map);
    System.out.println(e); //Employee(id=123, name=1.9, isGood=false, score=1.0, createTime=Tue Aug 15 12:34:41 CST 2023)

说明：

*  对于Integer、Float、Boolean类型，如果是null，则转成bean的属性后会变成默认值（0，0.1，false）
 *  对于Date类型，如果是null或者其他类型，转成bean的时候会报错，需要使用ConvertUtils进行类型转换（见下面）
 *  支持类型转换：比如Integer和String之间

**2）copyProperties：**

有另外一个对象（类型和Employee不同）

@Data
    public class Employee2 {
    	private Integer id;
    	private String name;
    	private String isGood;
    	private String score;
    	private String createTime;
    	private Float f1;
    }

测试

private static void test2_1() throws Exception {
            Employee ee = new Employee(null, "employee2", null, null, null);
            Employee2 e1 = new Employee2();
            BeanUtils.copyProperties(e1, ee);
            System.out.println(e1); //Employee2(id=null, name=employee2, isGood=null, score=null, createTime=null, f1=null)
            
            Employee ee2 = new Employee(1, "employee2", true, 4.3f, new Date());
            Employee2 e2 = new Employee2();
            BeanUtils.copyProperties(e2, ee2);
            System.out.println(e2); //Employee2(id=1, name=employee2, isGood=true, score=4.3, createTime=Tue Aug 15 11:45:06 CST 2023, f1=null)
    }

说明：

*  对于Integer、Float、Boolean、Date类型，如果是null，拷贝后也是null
 *  支持类型转换：两个bean只要属性名一样，类型可转换即可拷贝。比如Integer、Float、Boolean类型转成String

##### 2.2）PropertyUtils进行属性拷贝： #####

**1）和BeanUtils区别：**

*  PropertyUtils只支持两个Bean之间的属性拷贝，不支持Map到Bean的
 *  PropertyUtils在两个Bean之间进行属性拷贝时，必须要保证名字和类型都一样才行，否则会报错。BeanUtils在进行属性拷贝时，名字一样，类型可转换即可。

Employee ee = new Employee(null, "employee2", null, null, null);
    Employee2 e1 = new Employee2();
    PropertyUtils.copyProperties(e1, ee);
    System.out.println(e1); //Employee2(id=null, name=employee2, isGood=null, score=null, createTime=null, f1=null)
    
    Employee ee2 = new Employee(1, "employee2", true, 4.3f, new Date());
    Employee2 e2 = new Employee2();
    PropertyUtils.copyProperties(e2, ee2);
    System.out.println(e2); //报错

报错信息：

![7fb26714e3eb4cdd9ae73db2d65c4926.png][]

**2）说明：**

*  PropertyUtils不支持类型转换。
 *  对于null值，PropertyUtils拷贝后也是null

#### 3、ConvertUtils自定义类型转换 ####

**1）DateConverter：**

DateConverter继承DateTimeConverter，是beanutils包中自带的时间类型转换，包含了：![21511241f1de4f0f9f6c6d72fcb9b3d8.png][]

示例

DateConverter converter = new DateConverter();
    converter.setPattern("yyyy-MM-dd");
    ConvertUtils.register(converter, java.util.Date.class);
    
    Map<String, Object> map = new HashMap<>(5);
    map.put("id", 1); 
    map.put("name", "testConvertUtils");
    map.put("isGood", false); //可以是Integer或String，1或"1" true 其他表示false,null表示false
    map.put("score", 1.1f);
    map.put("createTime", "2023-08-15");
    map.put("add", "add1");
    
    // map > obj
    Employee e = new Employee();
    BeanUtils.populate(e, map);
    System.out.println(e); //Employee(id=1, name=testConvertUtils, isGood=false, score=1.1, createTime=Tue Aug 15 00:00:00 CST 2023)

**2）自定义：**

ConvertUtils.register(new Converter() {
        public Object convert(Class type, Object value) {
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            try {
                return simpleDateFormat.parse(value.toString());
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }
    }, Date.class);
    Employee e1 = new Employee();
    BeanUtils.setProperty(e1, "createTime", "2022-09-09");
    System.out.println(e1.getCreateTime()); //Fri Sep 09 00:00:00 CST 2022

说明：对于setProperty，如果存在时间类型，需要自定义转换器。

[7fb26714e3eb4cdd9ae73db2d65c4926.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/13/56803756306d4ab8998c05a315dff719.png
[21511241f1de4f0f9f6c6d72fcb9b3d8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/13/fed38f2993c14ca0a0137d91eb6ac34e.png