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

ftsr

//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