java中属性的类型

1.看代码,下面是一个类

下面主要红色字体部分的属性 

 package com.westsoft.serviceimpl;

import java.util.List;

import javax.annotation.Resource;
import javax.sql.DataSource;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import com.westsoft.bean.Person;
import com.westsoft.dao.PersonDao;
import com.westsoft.service.PersonService;

@Service @Transactional
public class PersonServiceBean implements PersonService {
    
    
    private JdbcTemplate jdbcTemplate;
    
    @Resource
    public void setJdbcTemplate(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }
    
    @Resource
    private PersonDao personDao;
    
    /*
    public PersonDao getPersonDao() {
        return personDao;
    }

    public void setPersonDao(PersonDao personDao) {
        this.personDao = personDao;
    }*/
    
    
    @Override
    public void delete(Integer id) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public Person getPerson(Integer id) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override @Transactional(propagation=Propagation.NOT_SUPPORTED)
    public List<Person> getPersons() {
        // TODO Auto-generated method stub
        return null;
    }

    /*
     * 新增
     * @Transactional(rollbackFor=Exception.class)
     * RuntimeException运行期例外,默认回滚
     * Exception 非运行期例外,不回滚
     * @Transactional(rollbackFor=Exception.class)
     * @Transactional(propagation=Propagation.NOT_SUPPORTED):不开启事务
     * @Transactional(propagation=Propagation.REQUIRED):默认事务行为,如果方法运行时已经处在一个事务中,则加入该事务,
     *                                                     否则为自己创建一个事务
     * @Transactional(propagation=Propagation.REQUIREDNEW):必须开启一个新事务,事务中嵌套事务
     
     *  @Transactional(propagation=Propagation.SUPPORTS):如果方法在已存在的事务中执行,则加入该事务,如果不在事务中执行,
     *                                                  则方法在没有事务的环境下执行.
     *  @Transactional(propagation=Propagation.MANDATORY):指定方法只能在已有的事务中执行,不会自动创建事务,如果没有在事务
     *                                                  中执行,则抛出异常.
     *  @Transactional(propagation=Propagation.NEVER):不能在事务中执行,否则抛出异常
     *  
     *  @Transactional(propagation=Propagation.NESTED):
     *  
     */
    @Override @Transactional(propagation=Propagation.REQUIRED)
    public void save(String name) throws Exception {
        // TODO Auto-generated method stub
        
        this.jdbcTemplate.update("insert into person(name) values(?)", new Object[]{name}, 
                    new int[]{java.sql.Types.VARCHAR});
        //throw new RuntimeException("运行期例外");
        
    }

    @Override
    public void update(Person person) {
        // TODO Auto-generated method stub
        
    }
}

 public void setJdbcTemplate(DataSource dataSource) {

        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

2.单元测试代码

     

        PropertyDescriptor[] ps = Introspector.getBeanInfo(PersonServiceBean.class).getPropertyDescriptors();
        for(PropertyDescriptor properdesc : ps){
            System.out.println(properdesc.getName()+":"+properdesc.getPropertyType());
        }
        

3.测试输出

 class:class java.lang.Class
jdbcTemplate:interface javax.sql.DataSource
persons:interface java.util.List

 根据输出的内容可以判断出属性的名称是jdbcTemplate,属性的数类型是javax.sql.DataSource

由此可见类的属性的类型并不是由属性所关联的字段的类型决定的,而是由传入的参数的类型决定的 

 4.如果有getAaa则属性的类型由getAaa的返回值决定,如下代码

 package com.westsoft.serviceimpl;

import java.util.List;

import javax.annotation.Resource;
import javax.sql.DataSource;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import com.westsoft.bean.Person;
import com.westsoft.dao.PersonDao;
import com.westsoft.service.PersonService;

@Service @Transactional
public class PersonServiceBean implements PersonService {
    
    
    private String bbb;
    
    
    
    
    public Integer getAaa() {
        return 0;
    }
    
    
    public void setAaa(Integer aaa) {
        this.bbb = (String)aaa.toString();
    }

    private JdbcTemplate jdbcTemplate;
    
    public JdbcTemplate getJdbcTemplate() {
        return this.jdbcTemplate ;
    }
    
    @Resource
    public void setJdbcTemplate(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }
    
    @Resource
    private PersonDao personDao;
    
    /*
    public PersonDao getPersonDao() {
        return personDao;
    }

    public void setPersonDao(PersonDao personDao) {
        this.personDao = personDao;
    }*/
    
    
    @Override
    public void delete(Integer id) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public Person getPerson(Integer id) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override @Transactional(propagation=Propagation.NOT_SUPPORTED)
    public List<Person> getPersons() {
        // TODO Auto-generated method stub
        return null;
    }

    /*
     * 新增
     * @Transactional(rollbackFor=Exception.class)
     * RuntimeException运行期例外,默认回滚
     * Exception 非运行期例外,不回滚
     * @Transactional(rollbackFor=Exception.class)
     * @Transactional(propagation=Propagation.NOT_SUPPORTED):不开启事务
     * @Transactional(propagation=Propagation.REQUIRED):默认事务行为,如果方法运行时已经处在一个事务中,则加入该事务,
     *                                                     否则为自己创建一个事务
     * @Transactional(propagation=Propagation.REQUIREDNEW):必须开启一个新事务,事务中嵌套事务
     
     *  @Transactional(propagation=Propagation.SUPPORTS):如果方法在已存在的事务中执行,则加入该事务,如果不在事务中执行,
     *                                                  则方法在没有事务的环境下执行.
     *  @Transactional(propagation=Propagation.MANDATORY):指定方法只能在已有的事务中执行,不会自动创建事务,如果没有在事务
     *                                                  中执行,则抛出异常.
     *  @Transactional(propagation=Propagation.NEVER):不能在事务中执行,否则抛出异常
     *  
     *  @Transactional(propagation=Propagation.NESTED):
     *  
     */
    @Override @Transactional(propagation=Propagation.REQUIRED)
    public void save(String name) throws Exception {
        // TODO Auto-generated method stub
        
        this.jdbcTemplate.update("insert into person(name) values(?)", new Object[]{name}, 
                    new int[]{java.sql.Types.VARCHAR});
        //throw new RuntimeException("运行期例外");
        
    }

    @Override
    public void update(Person person) {
        // TODO Auto-generated method stub
        
    }
}

5.测试输出 

 注意红色部分

 public Integer getAaa() {

        return 0;
    } 

publicvoid setAaa(Integer aaa) {
        this.bbb = (String)aaa.toString();
    }

 通过反射测试出属性的数据类型为

 aaa:class java.lang.Integer

class:class java.lang.Class
jdbcTemplate:class org.springframework.jdbc.core.JdbcTemplate
persons:interface java.util.List

 6.总结

在没有getAaa的情况下,属性的数据类型是有setAaa的传入参数决定,如果有getAaa则属性的数据类型有getAaa的返回类型决定.