BeanWrapper 是 Spring 框架中的一个接口，它提供了一种方式来设置和获取 JavaBean 的属性。JavaBean 是一种特殊的 Java 类，遵循特定的编码约定（例如，私有属性和公共的 getter/setter 方法），通常用于封装数据
主要功能
1.属性访问：
BeanWrapper 允许以统一的方式访问 JavaBean 对象的属性，包括简单属性、复杂类型属性、集合和数组等。它支持通过属性路径（property path）来访问嵌套对象的属性，例如 person.address.streetName。
2.类型转换：
BeanWrapper 内置了对常见类型的转换支持，可以自动处理不同数据类型的转换。
可以注册自定义的 PropertyEditor 或使用 ConversionService 来实现更复杂的类型转换逻辑。
3.属性编辑器：
可以为特定的数据类型注册 PropertyEditor，这允许在从字符串到对象或反之的转换过程中进行定制化处理。
4.错误处理：
当尝试设置非法值或访问不存在的属性时，BeanWrapper 可以捕获并报告这些错误。
访问简单属性
java
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
public class BeanWrapperExample {
public static void main(String[] args) {
// 创建一个目标对象
Person person = new Person();
// 创建 BeanWrapper 实例
BeanWrapper beanWrapper = new BeanWrapperImpl(person);
// 设置属性值
beanWrapper.setPropertyValue("name", "John Doe");
beanWrapper.setPropertyValue("age", 30);
// 获取属性值
String name = (String) beanWrapper.getPropertyValue("name");
int age = (Integer) beanWrapper.getPropertyValue("age");
System.out.println("Name: " + name);
System.out.println("Age: " + age);
}
}
class Person {
private String name;
private int age;
// 必须提供 getter 和 setter 方法
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}访问嵌套属性
java
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
public class NestedPropertyAccess {
public static void main(String[] args) {
Person person = new Person();
Address address = new Address();
person.setAddress(address);
BeanWrapper beanWrapper = new BeanWrapperImpl(person);
// 设置嵌套属性
beanWrapper.setPropertyValue("address.street", "123 Main St");
beanWrapper.setPropertyValue("address.city", "Springfield");
// 获取嵌套属性
String street = (String) beanWrapper.getPropertyValue("address.street");
String city = (String) beanWrapper.getPropertyValue("address.city");
System.out.println("Street: " + street); // 输出: Street: 123 Main St
System.out.println("City: " + city); // 输出: City: Springfield
}
}
class Person {
private String name;
private int age;
private Address address;
// Getters and Setters
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getAge() { return age; }
public void setAge(int age) { this.age = age; }
public Address getAddress() { return address; }
public void setAddress(Address address) { this.address = address; }
}
class Address {
private String street;
private String city;
// Getters and Setters
public String getStreet() { return street; }
public void setStreet(String street) { this.street = street; }
public String getCity() { return city; }
public void setCity(String city) { this.city = city; }
}自动类型转换
java
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
public class TypeConversion {
public static void main(String[] args) {
Person person = new Person();
BeanWrapper beanWrapper = new BeanWrapperImpl(person);
// 设置属性值，自动类型转换
beanWrapper.setPropertyValue("age", "30"); // 字符串 "30" 转换为 int 30
// 获取属性值
int age = (Integer) beanWrapper.getPropertyValue("age");
System.out.println("Age: " + age); // 输出: Age: 30
}
}
class Person {
private String name;
private int age;
// Getters and Setters
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getAge() { return age; }
public void setAge(int age) { this.age = age; }
}注册自定义 PropertyEditor
java
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import java.beans.PropertyEditorSupport;
public class CustomPropertyEditor {
public static void main(String[] args) {
Person person = new Person();
BeanWrapper beanWrapper = new BeanWrapperImpl(person);
// 注册自定义 PropertyEditor
beanWrapper.registerCustomEditor(Date.class, new DateEditor());
// 设置日期属性
beanWrapper.setPropertyValue("birthdate", "2023-01-01");
// 获取日期属性
Date birthdate = (Date) beanWrapper.getPropertyValue("birthdate");
System.out.println("Birthdate: " + birthdate);
// 输出: Birthdate: Sun Jan 01 00:00:00 CST 2023
}
}
class Person {
private String name;
private int age;
private Date birthdate;
// Getters and Setters
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getAge() { return age; }
public void setAge(int age) { this.age = age; }
public Date getBirthdate() { return birthdate; }
public void setBirthdate(Date birthdate) { this.birthdate = birthdate; }
}
class DateEditor extends PropertyEditorSupport {
@Override
public void setAsText(String text) throws IllegalArgumentException {
try {
setValue(new SimpleDateFormat("yyyy-MM-dd").parse(text));
} catch (ParseException e) {
throw new IllegalArgumentException("Invalid date format");
}
}
}处理属性设置错误
java
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.PropertyAccessException;
public class ErrorHandling {
public static void main(String[] args) {
Person person = new Person();
BeanWrapper beanWrapper = new BeanWrapperImpl(person);
try {
// 尝试设置一个不存在的属性
beanWrapper.setPropertyValue("invalidProperty", "value");
} catch (PropertyAccessException e) {
System.out.println("Error: " + e.getMessage());
// 输出: Error: Invalid property 'invalidProperty' of bean class [Person]:
// Bean property 'invalidProperty' is not readable or has an invalid getter
// method: Does the return type of the getter match the parameter type
// of the setter?
}
}
}
class Person {
private String name;
private int age;
// Getters and Setters
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getAge() { return age; }
public void setAge(int age) { this.age = age; }
}