一点小小的细节

今天看到一本书上写的,有关定义实体BEAN的一些细节,直到今天才知道其中的差别

代码如下:

java 代码1

/*
 * Test.java
 *
 * Created on 2006年12月15日, 上午12:06
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package com.hadeslee.entity;

import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

/**
 * Entity class Test
 *
 * @author lbf
 */
@Entity
public class Test implements Serializable {
    private Long id;
    private String name,sex,age;
    private int idCard;
    /** Creates a new instance of Test */
    public Test() {
    }

    /**
     * Gets the id of this Test.
     * @return the id
     */
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Long getId() {
        return this.id;
    }

    /**
     * Sets the id of this Test to the specified value.
     * @param id the new id
     */
    public void setId(Long id) {
        this.id = id;
    }
    public void setNameID(int ids){
        this.idCard=ids;
    }
    public int getNameID(){
        return idCard;
    }

    /**
     * Returns a hash code value for the object.  This implementation computes
     * a hash code value based on the id fields in this object.
     * @return a hash code value for this object.
     */
    @Override
    public int hashCode() {
        int hash = 0;
        hash += (this.id != null ? this.id.hashCode() : 0);
        return hash;
    }

    /**
     * Determines whether another object is equal to this Test.  The result is
     * <code>true</code> if and only if the argument is not null and is a Test object that
     * has the same id field values as this object.
     * @param object the reference object with which to compare
     * @return <code>true</code> if this object is the same as the argument;
     * <code>false</code> otherwise.
     */
    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Test)) {
            return false;
        }
        Test other = (Test)object;
        if (this.id != other.id && (this.id == null || !this.id.equals(other.id))) return false;
        return true;
    }

    /**
     * Returns a string representation of the object.  This implementation constructs
     * that representation based on the id fields.
     * @return a string representation of the object.
     */
    @Override
    public String toString() {
        return "com.hadeslee.entity.Test[id=" + id + "]";
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

}

java 代码2

/*
 * Test.java
 *
 * Created on 2006年12月15日, 上午12:06
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package com.hadeslee.entity;

import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

/**
 * Entity class Test
 *
 * @author lbf
 */
@Entity
public class Test implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name,sex,age;
    private int idCard;
    /** Creates a new instance of Test */
    public Test() {
    }

    /**
     * Gets the id of this Test.
     * @return the id
     */

    public Long getId() {
        return this.id;
    }

    /**
     * Sets the id of this Test to the specified value.
     * @param id the new id
     */
    public void setId(Long id) {
        this.id = id;
    }
    public void setNameID(int ids){
        this.idCard=ids;
    }
    public int getNameID(){
        return idCard;
    }

    /**
     * Returns a hash code value for the object.  This implementation computes
     * a hash code value based on the id fields in this object.
     * @return a hash code value for this object.
     */
    @Override
    public int hashCode() {
        int hash = 0;
        hash += (this.id != null ? this.id.hashCode() : 0);
        return hash;
    }

    /**
     * Determines whether another object is equal to this Test.  The result is
     * <code>true</code> if and only if the argument is not null and is a Test object that
     * has the same id field values as this object.
     * @param object the reference object with which to compare
     * @return <code>true</code> if this object is the same as the argument;
     * <code>false</code> otherwise.
     */
    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Test)) {
            return false;
        }
        Test other = (Test)object;
        if (this.id != other.id && (this.id == null || !this.id.equals(other.id))) return false;
        return true;
    }

    /**
     * Returns a string representation of the object.  This implementation constructs
     * that representation based on the id fields.
     * @return a string representation of the object.
     */
    @Override
    public String toString() {
        return "com.hadeslee.entity.Test[id=" + id + "]";
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

}

代码1和代码2唯一的差别就是@Id的注释地方不同了

同样是注释主键,当在直接用在变量上注释时,如果其它的成员变量没有指定名字,则数据库生成的表的各列名字将以定义的成员变量的变量名为准

当用在getter方法注释时,则数据库生成的表的各列名字将取getXXXX的XXXX名字,将不再取定义的成员变量名

像上面的例子中,代码1会有IdCard这一列,则代码2取而代之的将是NameID这一列.这看上去是一个小小的差别,但是了解了终究是好事.呵呵.终于懂清楚在get上注释和直接在成员变量上注释的差别了,一般来说是不会有什么差别的,一般标准 的JAVABEAN都是成员变量名和getter,setter签名一样的.

好了,睡觉去了