java - 如何从 JavaBean(域类)中的属性文件读取值？

Question

我有一个域类，我想从属性文件中读取值( Autowiring messageSource 在这里不起作用)，所以有什么想法吗？我正在使用 spring、hibernate这是一个示例:

package com.myapp.domain;

import java.io.Serializable;

import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;


@SuppressWarnings("serial")
@Entity
@Table(name = "domain")
public class MyDomain implements Serializable {

    private long entityId;
    private String domain="some_hardcoded_value" // need to read it from a property file;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    @Basic(fetch = FetchType.EAGER)
    public long getEntityId() {
        return entityId;
    }

    public void setEntityId(long entityId) {
        this.entityId = entityId;
    }

    public void setDomain(String domain) {
        this.domain = domain;
    }

    @Column(name = "domain")
    public String getDomain() {
        return domain;
    }

}

Answer 1

我仍然不明白这个问题，但我假设您想从属性文件设置 bean 属性。

其他答案已经展示了如何从 .properties 文件获取 Properties 对象(我将在下面展示其他方法)，我将向您展示如何使用 Spring 的 BeanWrapper 接口(interface)从中连接属性:

public static void wireBeanFromProperties(Object bean, Properties props){

    BeanWrapper wrapper = new BeanWrapperImpl(bean);
    for(Entry<Object, Object> entry:props.entrySet()){
        String propertyName = entry.getKey().toString();
        if(wrapper.isWritableProperty(propertyName)){
            wrapper.setPropertyValue(propertyName, entry.getValue());
        }
    }

}

或者，如果您确定属性文件中的所有属性都可以映射到该类的此 bean 属性:

public static void wireBeanFromProperties(final Object bean,
    final Properties props){
    final BeanWrapper wrapper = new BeanWrapperImpl(bean);
    // will throw an exception if the Properties object
    // contains any unknown keys
    wrapper.setPropertyValues(props);
}

引用:5.4. Bean manipulation and the BeanWrapper

<小时/>

实际上，Spring 特有的从类路径加载资源的方法使用 the Resource mechanism

InputStream str = new ClassPathResource("classpath:some.properties")
                      .getInputStream();

最好的一点是，您可以使用 classpath: 语法从 XML 轻松连接 InputStreams 和资源:

Java代码

private InputStream stream;
private Resource resource;
public void setStream(InputStream stream){
    this.stream = stream;
}
public void setResource(Resource resource){
    this.resource = resource;
}

属性接线:

<bean class="MyClass">
    <property name="stream" value="classpath:file1.properties" />
    <property name="resource" value="classpath:file2.properties" />
</bean>

<小时/>

如果您只想初始化静态最终字段，请按以下步骤操作:

private static final String DOMAIN;
static{
    InputStream inputStream=null;
    try{
        inputStream = new ClassPathResource("classpath:some.properties")
                          .getInputStream();
        Properties props = new Properties();
        props.load(inputStream);
        String key = "your.property";
        if(!props.containsKey(key))
            throw new IllegalStateException("Property not found");
        DOMAIN= props.getProperty(key);
    } catch(IOException e){
        throw new IllegalStateException(e);
    }finally{
        // apache commons / IO
        IOUtils.closeQuietly(inputStream);
    }
}