Mastering Spring Boot 3 BeanWrapper: Real-World Cases & Code Walkthrough

1. Introduction

In Java development, handling object properties (getting, setting, querying) is common but often requires repetitive code. Spring's BeanWrapper class offers an elegant solution by abstracting property access, supporting nested properties, batch setting, and metadata queries.

2. Practical Cases

2.1 Basic Usage

BeanWrapper instanceWrapper = new BeanWrapperImpl(User.class);
instanceWrapper.setPropertyValue("id", 666L);
instanceWrapper.setPropertyValue("name", "Pack");
Object instance = instanceWrapper.getWrappedInstance();
System.err.println(instance);

2.2 Using Map to Bind Data

BeanWrapper instanceWrapper = new BeanWrapperImpl(User.class);
Map<String, Object> data = new HashMap<>();
data.put("id", "8888");
data.put("name", "Pack");
instanceWrapper.setPropertyValues(data);
Object instance = instanceWrapper.getWrappedInstance();
System.err.println(instance);

2.3 Using PropertyValue to Bind Data

BeanWrapper instanceWrapper = ...;
MutablePropertyValues pvs = new MutablePropertyValues();
PropertyValue pv = new PropertyValue("id", "8888");
pvs.addPropertyValue(pv);
instanceWrapper.setPropertyValues(pvs);

2.4 Binding Nested Objects

BeanWrapper instanceWrapper = ...;
Map<String, Object> data = new HashMap<>();
data.put("id", "8888");
data.put("name", "Pack");
data.put("address.province", "新疆");
instanceWrapper.setPropertyValues(data);
Object instance = instanceWrapper.getWrappedInstance();
System.err.println(instance);

2.5 Collection Property Binding

public class User {
    // ...
    private List<String> hobby = new ArrayList<>();
}
BeanWrapper instanceWrapper = ...;
Map<String, Object> data = ...;
data.put("hobby[0]", "足球");
data.put("hobby[1]", "篮球");
instanceWrapper.setPropertyValues(data);
Object instance = instanceWrapper.getWrappedInstance();
System.err.println(instance);

2.6 Data Type Conversion

By default, BeanWrapper cannot convert enum values automatically. A custom converter can be registered:

public class GenderConverter implements Converter<String, GenderEnum> {
    @Override
    public GenderEnum convert(String source) {
        if (source == null) return null;
        try {
            int code = Integer.parseInt(source);
            return GenderEnum.fromCode(code);
        } catch (Exception e) {
            return null;
        }
    }
}
BeanWrapper instanceWrapper = new BeanWrapperImpl(User.class);
DefaultFormattingConversionService conversionService = new DefaultFormattingConversionService();
conversionService.addConverter(new GenderConverter());
instanceWrapper.setConversionService(conversionService);
Map<String, Object> data = new HashMap<>();
data.put("name", "Pack");
data.put("gender", "1");
instanceWrapper.setPropertyValues(data);
Object instance = instanceWrapper.getWrappedInstance();
System.err.println(instance);

2.7 Binding HTTP Request Parameters

// Simulate ServletRequest
MockHttpServletRequest request = new MockHttpServletRequest();
request.setParameter("id", "888");
request.setParameter("name", "Spring Boot3实战案例200讲");
request.setParameter("hobby[0]", "足球");
request.setParameter("hobby[1]", "篮球");
BeanWrapper instanceWrapper = ...;
PropertyValues pvs = new ServletRequestParameterPropertyValues(request);
instanceWrapper.setPropertyValues(pvs);
Object instance = instanceWrapper.getWrappedInstance();
System.err.println(instance);

2.8 Accessing Property Values

Properties can be read using BeanWrapper#getPropertyValue and its overloads. Common expressions:

Expression

Explanation name Corresponds to getName() or isName() and setName(..). account.name Nested property, equivalent to getAccount().getName() or setName(..) on the nested object. accounts[2] Indexed property, the third element of a list/array named accounts. accounts[KEY] Key‑based index, maps a key to a value in a collection.

2.9 Getting Property Metadata

For dynamic analysis (e.g., form generation, API docs), BeanWrapper can expose PropertyDescriptor objects:

BeanWrapper wrapper = new BeanWrapperImpl(User.class);
Arrays.asList(wrapper.getPropertyDescriptors()).forEach(pd -> {
    System.err.println("name: " + pd.getName() + ", type: " + pd.getPropertyType()
        + ", 
readMethod: " + pd.getReadMethod()
        + ", 
writeMethod: " + pd.getWriteMethod());
    System.out.println("-------------------------------");
});