一 、BeanUtils组件
1.1 引入
1.1.1 简介
程序中对javabean的操作很频繁, 所以apache提供了一套开源的api,方便对
javabean的操作!即BeanUtils组件。
BeanUtils组件: 作用是简化javabean的操作!
1.1.2 使用BenUtils组件前提
使用BenUtils组件:
1.引入commons-beanutils-1.8.3.jar核心包
2.引入日志支持包: commons-logging-1.1.3.jar
注意:
需要导入两个包,一个是beanutils组件包,另外一个是日志包。
由于beanutils组件内部以来了日志包,所以缺少日志包,会报错。
如果缺少日志jar文件,报错:
java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
at org.apache.commons.beanutils.ConvertUtilsBean.<init>(ConvertUtilsBean.java:157)
at org.apache.commons.beanutils.BeanUtilsBean.<init>(BeanUtilsBean.java:117)
at org.apache.commons.beanutils.BeanUtilsBean$1.initialValue(BeanUtilsBean.java:68)
1.2 BeanUtils组件的API
方法1: 设置对象的属性值
BeanUtils.copyProperty(admin, "userName", "jack");
BeanUtils.setProperty(admin, "age", 18);
注意:
使用BeanUtils组件设置对象的属性值时候,对于属性的类型会自动转化。
eg:BeanUtils.copyProperty(admin, "age", "12");
BeanUtils.copyProperty(admin, "age", 12);
上面两种方式够可以给int类型的age赋值。
使用BeanUtils设置对象的属性值时,可以不考虑值得类型,它内部会自动转换。
方法2: 拷贝对象
BeanUtils.copyProperties(newAdmin, admin);
注意:使用BeanUtils组件拷贝对象时,如果对象中维护了另外一个对象,拷贝的也只是该对象的引用。
方法3: 将map转为javaBean
BeanUtils.populate(adminMap, map);
注意:map中的key要与javabean的属性名称一致
1.2.1 设置对象的属性值
设置对象的属性值,对于简单类型的属性,类型会自动转换。
/**
* 设置对象的属性
*
* @throws IllegalAccessException
* @throws InvocationTargetException
*/
private static void test1() throws IllegalAccessException, InvocationTargetException {
//设置对象的属性
Student s=new Student();
BeanUtils.copyProperty(s, "name", "小白");
//设置对象的属性值,对于简单类型的属性,类型会自动转换。
BeanUtils.copyProperty(s, "age","12");
//BeanUtils.copyProperty(s, "age",12);
BeanUtils.copyProperty(s, "birth",new Date());
System.out.println(s.getName());
System.out.println(s.getBirth());
}
1.2.2 拷贝对象
1.如果被拷贝的对象有date类型的属性时,
那么必须实现Date自定义类型转换器。
如果没有实现,那么该属性必须赋值,否则拷贝会报错。
2.被拷贝的对象内部维护另外一个对象,拷贝时,也只是拷贝了内部维护的
对象的引用,即内存地址。
例1:被拷贝的对象由date类型的属性,没有设置自定义类型转换器,也没有赋值,拷贝时就会报错。
private static void test2() throws IllegalAccessException, InvocationTargetException {
Student s=new Student();
s.setName("小白");
s.setAge(12);
//s.setBirth(new Date());
Student s2=new Student();
BeanUtils.copyProperties(s2, s);
}
例2:拷贝的对象内部维护另外一个对象,拷贝时,也只是拷贝了内部维护的对象的引用,即内存地址。
private static void test2() throws IllegalAccessException, InvocationTargetException {
Student s=new Student();
s.setName("小白");
s.setAge(12);
s.setBirth(new Date());
User u=new User();
u.setAge(12);
u.setName("小黑");
//学生对象中维护了用户对象。
s.setU(u);
//将s对象拷贝到s2对象
Student s2=new Student();
BeanUtils.copyProperties(s2, s);
System.out.println(s2.getU()==u); // true
}
1.2.3 将map转为javaBean
private static void test3() throws IllegalAccessException, InvocationTargetException {
Map map=new HashMap();
map.put("name", "小白");
map.put("age", "12");
map.put("birth", new Date());
//将map转换为bean
Student s=new Student();
BeanUtils.populate(s, map);
System.out.println(s.getName());
System.out.println(s.getBirth());
}
1.2.4 自定义类型转换器(自定义Date类型转换器)
自定义date类型的类型转换器
private static void test4() throws IllegalAccessException, InvocationTargetException {
Map map=new HashMap();
map.put("name", "小白");
map.put("age", "12");
map.put("birth", "2019-01-01");
//自定义date类型转换器
ConvertUtils.register(new Converter() {
@Override
public Object convert(Class clazz, Object value) {
if(value==null||"".equals(value.toString().trim())) {
return null;
}
try {
String str=(String)value;
SimpleDateFormat sd=new SimpleDateFormat("yyyy-MM-dd");
return sd.parse(str);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
}, Date.class);
//将map转化为bean
Student s=new Student();
BeanUtils.populate(s, map);
System.out.println(s.getBirth());
}
使用组件自带的date类型转换器
private static void test4() throws IllegalAccessException, InvocationTargetException {
Map map=new HashMap();
map.put("name", "小白");
map.put("age", "12");
map.put("birth", "2019-01-01");
//使用系统自带的date类型转换器
ConvertUtils.register(new DateLocaleConverter(), Date.class);
//将map转化为bean
Student s=new Student();
BeanUtils.populate(s, map);
System.out.println(s.getBirth());
}
1.3 使用BeanUtils组件封装请求参数(BeanUtils组件的应用场景)
获取请求参数时,我们要逐一获取,比较麻烦,
所以可以使用BenaUtils组件,封装请求参数到实体对象。
切记:实体对象的属性名一个要和表单的name名称相同。
1.3.1 使用BeanUtils组件封装请求参数(基础版本)
HelloWorld .java
public class HelloWorld extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//String username = req.getParameter("username");
//String pwd = req.getParameter("pwd");
Enumeration<String> ens = req.getParameterNames();
UserParamter userParamter=new UserParamter();
while(ens.hasMoreElements()) {
String key = ens.nextElement();
String value = req.getParameter(key);
try {
BeanUtils.setProperty(userParamter, key, value);
} catch (IllegalAccessException | InvocationTargetException e) {
throw new RuntimeException(e);
}
}
System.out.println("username:"+userParamter.getUsername());
System.out.println("pwd:"+userParamter.getPwd());
}
}
UserParamter.java 封装请求参数的实体类
public class UserParamter {
private String username;
private String pwd;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
}
index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/hello" method="post">
<input type="text" name="username">
<input type="text" name="pwd">
<input type="submit" value="提交">
</form>
</body>
</html>
浏览器访问indexjsp,并提交
控制台打印:
1.3.2 使用BeanUtils组件封装请求参数(升级版本1.2)
RequestUtil.java 封装的工具类
public class RequestUtil {
public static <T> T converToBean(HttpServletRequest req,Class<T> clazz) {
T item=null;
try {
item = clazz.newInstance();
Map<String, String[]> map = req.getParameterMap();
BeanUtils.populate(item, map);
} catch (Exception e1) {
e1.printStackTrace();
}
return item;
}
}
测试:
HelloWorld .java
public class HelloWorld extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//String username = req.getParameter("username");
//String pwd = req.getParameter("pwd");
UserParamter userParamter = RequestUtil.converToBean(req, UserParamter.class);
System.out.println("username:"+userParamter.getUsername());
System.out.println("pwd:"+userParamter.getPwd());
}
}
1.3.3 使用BeanUtils组件封装请求参数(升级版本1.2)
RequestUtil.java 封装的工具类
public class RequestUtil {
public static <T> T converToBean(HttpServletRequest req,Class<T> clazz) {
T item=null;
try {
item = clazz.newInstance();
Enumeration<String> ens = req.getParameterNames();
while(ens.hasMoreElements()) {
String key = ens.nextElement();
String value = req.getParameter(key);
try {
BeanUtils.setProperty(item, key, value);
} catch (IllegalAccessException | InvocationTargetException e) {
throw new RuntimeException(e);
}
}
} catch (InstantiationException | IllegalAccessException e1) {
e1.printStackTrace();
}
return item;
}
}
测试:
HelloWorld .java
public class HelloWorld extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//String username = req.getParameter("username");
//String pwd = req.getParameter("pwd");
UserParamter userParamter = RequestUtil.converToBean(req, UserParamter.class);
System.out.println("username:"+userParamter.getUsername());
System.out.println("pwd:"+userParamter.getPwd());
}
}
//1. 对javabean的基本操作
@Test
public void test1() throws Exception {
// a. 基本操作
Admin admin = new Admin();
// admin.setUserName(“Jack”);
// admin.setPwd(“999”);
// b. BeanUtils组件实现对象属性的拷贝
BeanUtils.copyProperty(admin, "userName", "jack");
BeanUtils.setProperty(admin, "age", 18);
// 总结1: 对于基本数据类型,会自动进行类型转换!
// c. 对象的拷贝
Admin newAdmin = new Admin();
BeanUtils.copyProperties(newAdmin, admin);
// d. map数据,拷贝到对象中
Admin adminMap = new Admin();
Map<String,Object> map = new HashMap<String,Object>();
map.put("userName", "Jerry");
map.put("age", 29);
// 注意:map中的key要与javabean的属性名称一致
BeanUtils.populate(adminMap, map);
// 测试
System.out.println(adminMap.getUserName());
System.out.println(adminMap.getAge());
}