org.apache.commons.lang.builder——ToStringBuilder类

//本示例来自Jakarta Commons Cookbook   
public class PoliticalCandidate {   
  
    private String lastName;   
  
    private String firstName;   
  
    private Date dateOfBirth;   
  
    private BigDecimal moneyRaised;   
  
    private State homeState;   
  
  
    // get/set methods 省略   
  
  
    public void toString( ) {   
  
        return new ToStringBuilder(this,  ToStringStyle.MULTI_LINE_STYLE)

                   .append("lastName", lastName)

                   .append("firstName", firstName)

                   .toString( );

  
    }   
  
}  

//结果输出
com.discursive.jccook.lang.builders.PoliticalCandidate@1cd2e5f[

  lastName=Jefferson

  firstName=Thomas

]

//下面是几个默认的style的打印结果
ToStringStyle.DEFAULT_STYLE

com.discursive.jccook.lang.builders.

PoliticalCandidate@1cd2e5f[lastName=Jefferson,firstName=Thomas]


ToStringStyle.MULTI_LINE_STYLE

com.discursive.jccook.lang.builders.PoliticalCandidate@1cd2e5f[

  lastName=Jefferson

  firstName=Thomas

]


ToStringStyle.NO_FIELD_NAMES_STYLE

com.discursive.jccook.lang.builders.PoliticalCandidate@1cd2e5f[Jefferson,Thomas]


ToStringStyle.SIMPLE_STYLE

Jefferson,Thomas

 

像NO_FIELD_NAMES_STYLE，SIMPLE_STYLE这些都是ToStringTyle的内部类，继承自ToStringStyle，重写了一些属性。

下面看一下ToStringBuilder的源码：

package org.apache.commons.lang.builder;

import org.apache.commons.lang.BooleanUtils;
import org.apache.commons.lang.ObjectUtils;

public class ToStringBuilder {

   //默认的样式
    private static ToStringStyle defaultStyle = ToStringStyle.DEFAULT_STYLE;

    public static ToStringStyle getDefaultStyle() {
        return defaultStyle;
    }
   
  //下面几个方法都是简单的调用ReflectionToStringBuilder的toString方法
    public static String reflectionToString(Object object) {
        return ReflectionToStringBuilder.toString(object);
    }

    public static String reflectionToString(Object object, ToStringStyle style) {
        return ReflectionToStringBuilder.toString(object, style);
    }

    public static String reflectionToString(Object object, ToStringStyle style, boolean outputTransients) {
        return ReflectionToStringBuilder.toString(object, style, outputTransients, false, null);
    }

    public static String reflectionToString(
        Object object,
        ToStringStyle style,
        boolean outputTransients,
        Class reflectUpToClass) {
        return ReflectionToStringBuilder.toString(object, style, outputTransients, false, reflectUpToClass);
    }

    public static void setDefaultStyle(ToStringStyle style) {
        if (style == null) {
            throw new IllegalArgumentException("The style must not be null");
        }
        defaultStyle = style;
    }

   //最后输出的字符串缓存
    private final StringBuffer buffer;

    private final Object object;

    private final ToStringStyle style;

    public ToStringBuilder(Object object) {
        this(object, getDefaultStyle(), null);
    }

    public ToStringBuilder(Object object, ToStringStyle style) {
        this(object, style, null);
    }

    public ToStringBuilder(Object object, ToStringStyle style, StringBuffer buffer) {
        if (style == null) {
            style = getDefaultStyle();
        }
        if (buffer == null) {
            buffer = new StringBuffer(512);
        }
        this.buffer = buffer;
        this.style = style;
        this.object = object;
//这里append上开始字符
        style.appendStart(buffer, object);
    }

     //ToStringBuilder中的append方法都是委托给ToStringStyle进行处理的
   //并且返回一个ToStringBuilder实例，这样就可以进行链式操作了。
   //例如：new ToStringBuilder().append().append().append()......

    public ToStringBuilder append(boolean value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(boolean[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(byte value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(byte[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(char value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(char[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(double value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(double[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(float value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(float[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(int value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(int[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(long value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(long[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(Object obj) {
        style.append(buffer, null, obj, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(Object[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(short value) {
        style.append(buffer, null, value);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder append(short[] array) {
        style.append(buffer, null, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, boolean value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, boolean[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, boolean[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, byte value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, byte[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, byte[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, char value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, char[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, char[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, double value) {
        style.append(buffer, fieldName, value);
        return this;
    }
    
    public ToStringBuilder append(String fieldName, double[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, double[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, float value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, float[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, float[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, int value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, int[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, int[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, long value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, long[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, long[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, Object obj) {
        style.append(buffer, fieldName, obj, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, Object obj, boolean fullDetail) {
        style.append(buffer, fieldName, obj, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, Object[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, Object[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }

    public ToStringBuilder append(String fieldName, short value) {
        style.append(buffer, fieldName, value);
        return this;
    }

    public ToStringBuilder append(String fieldName, short[] array) {
        style.append(buffer, fieldName, array, null);
        return this;
    }

    public ToStringBuilder append(String fieldName, short[] array, boolean fullDetail) {
        style.append(buffer, fieldName, array, BooleanUtils.toBooleanObject(fullDetail));
        return this;
    }
   //appendIdentityToString是一个被deprecated的方法，它的作用就是返回一个对象的类型+hashcode的字符串
    public ToStringBuilder appendAsObjectToString(Object object) {
        ObjectUtils.appendIdentityToString(this.getStringBuffer(), object);
        return this;
    }

    //----------------------------------------------------------------------------

    public ToStringBuilder appendSuper(String superToString) {
        if (superToString != null) {
            style.appendSuper(buffer, superToString);
        }
        return this;
    }

    public ToStringBuilder appendToString(String toString) {
        if (toString != null) {
            style.appendToString(buffer, toString);
        }
        return this;
    }

    public Object getObject() {
        return object;
    }

    public StringBuffer getStringBuffer() {
        return buffer;
    }

    //----------------------------------------------------------------------------

    public ToStringStyle getStyle() {
        return style;
    }

//最后append上结束字符，并返回最后的格式字符串
    public String toString() {
        if (this.getObject() == null) {
            this.getStringBuffer().append(this.getStyle().getNullText());
        } else {
            style.appendEnd(this.getStringBuffer(), this.getObject());
        }
        return this.getStringBuffer().toString();
    }

}

 

 

我们可以看到非常清楚的SRP（单一职责原则）的应用。ToStringBuilder就是负责存储字符串，至于应该以什么格式存储字符串，则交给ToStringStyle去完成。所以这个类的大部分工作都委托给了ToStringStyle