Guava记录 - MoreObjects.toStringHe

java中object的toString()方法咱使用的也比较频繁，常见的场景如：使用log4j等输出日志对象的时候，会调用对象的toString()方法。而object的toString()方法默认实现如下：

/**
     * Returns a string representation of the object. In general, the
     * {@code toString} method returns a string that
     * "textually represents" this object. The result should
     * be a concise but informative representation that is easy for a
     * person to read.
     * It is recommended that all subclasses override this method.
     * <p>
     * The {@code toString} method for class {@code Object}
     * returns a string consisting of the name of the class of which the
     * object is an instance, the at-sign character `{@code @}', and
     * the unsigned hexadecimal representation of the hash code of the
     * object. In other words, this method returns a string equal to the
     * value of:
     * <blockquote>
     * <pre>
     * getClass().getName() + '@' + Integer.toHexString(hashCode())
     * </pre></blockquote>
     *
     * @return  a string representation of the object.
     */
    public String toString() {
        return getClass().getName() + "@" + Integer.toHexString(hashCode());
    }

因此，咱通常会在对象中重写对象的toString()方法，比如得到一个json串之类的，如下:

/**
 * @author ying.pan
 * @date 2019/9/16 11:41 AM.
 */
public class MoreObj implements Serializable {
    /**
     * test value
     */
    private String value;
    /**
     * test text
     */
    private String text;

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    @Override
    public String toString() {
        return reflectionToString(this, JSON_STYLE);
    }
}

MoreObjects对象提供了toStringHelper()方法，使我们可以更加便捷的实现指定的toString()方法,大致用法如下：

    private static void testMoreObjectsToString() {
        MoreObj moreObj = new MoreObj();
        moreObj.setText("text");
        moreObj.setValue("value");
        //step1 测试输出默认object toString方法
        System.out.println("重写toString(),返回json格式:  "+moreObj.toString());

        //step2 测试toStringHelper(),传入.class
        //第一个 params为key,第二个params为 value
        System.out.println("使用toStringHelper(),clazz:   "+MoreObjects.toStringHelper(MoreObj.class).add(moreObj.getValue(), "test value")
                .add(moreObj.getValue(), "test value").toString());

        //step3 测试toStringHelper(),传入self Obj
        //第一个 params为key,第二个params为 value
        System.out.println("使用toStringHelper(),self object:   "+MoreObjects.toStringHelper(moreObj).add(moreObj.getValue(), "test value")
                .add(moreObj.getValue(), "test value").toString());
    }

输出结果:

值得一说的是: MoreObjects.toStringHelper(xx).add(key,value)支持重复的(k,v);

toStringHelper的时候会返回一个ToStringHelper，至于里面包含的内容以及最终MoreObjects的toString()的具体实现，感兴趣的小伙伴可以自己去发现哦，也许能看见一些有趣的事情.......