[Jakarta Commons笔记] 代码范例 - BeanUtils

假定我们有如下两个标准的JavaBean：



/** Address.java */



package sean.study.commons.beanutils;



public class Address {



    private String zipCode;

    private String addr;

    private String city;

    private String country;



    public Address() {

    }



    public Address(String zipCode, String addr, String city, String country) {

        this.zipCode = zipCode;

        this.addr = addr;

        this.city = city;

        this.country = country;

    }



    public String getAddr() {

        return addr;

    }



    public void setAddr(String addr) {

        this.addr = addr;

    }



    public String getCity() {

        return city;

    }



    public void setCity(String city) {

        this.city = city;

    }



    public String getCountry() {

        return country;

    }



    public void setCountry(String country) {

        this.country = country;

    }



    public String getZipCode() {

        return zipCode;

    }



    public void setZipCode(String zipCode) {

        this.zipCode = zipCode;

    }



}



/** Customer.java */



package sean.study.commons.beanutils;



public class Customer {



    private long id;

    private String name;

    private Address[] addresses;



    public Customer() {

    }



    public Customer(long id, String name, Address[] addresses) {

        this.id = id;

        this.name = name;

        this.addresses = addresses;

    }



    public Address[] getAddresses() {

        return addresses;

    }



    public void setAddresses(Address[] addresses) {

        this.addresses = addresses;

    }



    public long getId() {

        return id;

    }



    public void setId(long id) {

        this.id = id;

    }



    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



}





我们来看看通常我们是怎样利用Commons BeanUtils来完成一些基本的JavaBean和DynaBean操作：



package sean.study.commons.beanutils;



import org.apache.commons.beanutils.BasicDynaBean;

import org.apache.commons.beanutils.BasicDynaClass;

import org.apache.commons.beanutils.DynaBean;

import org.apache.commons.beanutils.DynaProperty;

import org.apache.commons.beanutils.PropertyUtils;

import org.apache.commons.lang.StringUtils;



public class BeanUtilsUsage {



    public static void main(String[] args) throws Exception {

        demoNormalJavaBeans();

        demoDynaBeans();

    }



    public static void demoNormalJavaBeans() throws Exception {



        System.out.println(StringUtils.center(" demoNormalJavaBeans ", 40, "="));

       

        // data setup

        Address addr1 = new Address("CA1234", "xxx", "Los Angeles", "USA");

        Address addr2 = new Address("100000", "xxx", "Beijing", "China");

        Address[] addrs = new Address[2];

        addrs[0] = addr1;

        addrs[1] = addr2;

        Customer cust = new Customer(123, "John Smith", addrs);

       

        // accessing the city of first address

        String cityPattern = "addresses[0].city";

        String name = (String) PropertyUtils.getSimpleProperty(cust, "name");

        String city = (String) PropertyUtils.getProperty(cust, cityPattern);

        Object[] rawOutput1 = new Object[] { "The city of customer ", name,

                "'s first address is ", city, "." };

        System.out.println(StringUtils.join(rawOutput1));

       

        // setting the zipcode of customer's second address

        String zipPattern = "addresses[1].zipCode";

        if (PropertyUtils.isWriteable(cust, zipPattern)) {

            System.out.println("Setting zipcode ...");

            PropertyUtils.setProperty(cust, zipPattern, "200000");

        }

        String zip = (String) PropertyUtils.getProperty(cust, zipPattern);

        Object[] rawOutput2 = new Object[] { "The zipcode of customer ", name,

                "'s second address is now ", zip, "." };

        System.out.println(StringUtils.join(rawOutput2));

       

        System.out.println();

    }



    public static void demoDynaBeans() throws Exception {



        System.out.println(StringUtils.center(" demoDynaBeans ", 40, "="));

       

        // creating a DynaBean

        DynaProperty[] dynaBeanProperties = new DynaProperty[] {

                new DynaProperty("name", String.class),

                new DynaProperty("inPrice", Double.class), 

                new DynaProperty("outPrice", Double.class),

        };

        BasicDynaClass cargoClass = new BasicDynaClass("Cargo", BasicDynaBean.class, dynaBeanProperties);

        DynaBean cargo = cargoClass.newInstance();

       

        // accessing a DynaBean

        cargo.set("name", "Instant Noodles");

        cargo.set("inPrice", new Double(21.3));

        cargo.set("outPrice", new Double(23.8));

        System.out.println("name: " + cargo.get("name"));

        System.out.println("inPrice: " + cargo.get("inPrice"));

        System.out.println("outPrice: " + cargo.get("outPrice"));



        System.out.println();

    }



}



上述代码运行结果如下：



========= demoNormalJavaBeans ==========

The city of customer John Smith's first address is Los Angeles.

Setting zipcode ...

The zipcode of customer John Smith's second address is now 200000.



============ demoDynaBeans =============

name: Instant Noodles

inPrice: 21.3

outPrice: 23.8



以上代码简单说明了一下BeanUtils常见的基本用法，还有很多高阶或者更具体的应用及原理，这里无法一一讲到，而且有很多笔者也不熟悉、不了解，对BeanUtils的讲解就到此吧。如果你有兴趣，或者还不是很清楚为什么像这样动态的或者说松散的访问JavaBean是有必要的，可以把Struts的源码拿下来研究一下，看看FormBean以及DynaActionForm这些是如何被动态创建的，一定会有收获。