Definition of the Builder pattern
- A Builder Pattern separates the construction of a complex object from its representation, allowing the same construction process to create different representations.
- Features: The user only needs to specify the type to be built to obtain the object, the construction process and details do not need to know
- Belongs to the creation pattern
Scenarios where the Builder pattern applies
- There are many steps that apply to creating objects, but the order of steps is not necessarily fixed
- If an object has a very complex internal structure (many properties)
- Separate the creation of load objects from their application
Advantages of the Builder pattern
- Good encapsulation, create and apply separation
- Good scalability, build classes are independent and decoupled to some extent
Disadvantages of the Builder model
- Creates redundant Builder objects
- Changes within the product require modification by the builder, which is costly
The builder pattern is embodied in the source code
- The JDK: StringBuilder
- Mybatis: CacheBulider, SqlSessionFactory
- Spring: BeanDefinitionBuilder
The difference between builder mode and factory mode
- The builder pattern focuses more on methods and order of invocation, while the factory pattern focuses on creating objects
- The intensity of object creation varies. The builder pattern creates complex objects, consisting of complex parts, while the factory pattern creates the same
- Concern: The factory pattern only needs to create the object. The builder pattern does not need to create the object, but also needs to know what parts the object consists of
- The builder pattern is different depending on the order in which the object is built
Chained programming example 1
import lombok.Data; public class CourseBuilder { private Course course = new Course(); public CourseBuilder addName(String name) { course.setName(name); return this; } public CourseBuilder addPPT(String ppt) { course.setPpt(ppt); return this; } public CourseBuilder addVideo(String video) { course.setVideo(video); return this; } public CourseBuilder addNote(String note) { course.setNote(note); return this; } public CourseBuilder addHomework(String homework) { course.setHomework(homework); return this; } public Course build() { return this.course; } @Data public class Course { private String name; private String ppt; private String video; private String note; private String homework; @Override public String toString() { return "CourseBuilder{" + "name='" + name + '\'' + ", ppt='" + ppt + '\'' + ", video='" + video + '\'' + ", note='" + note + '\'' + ", homework='" + homework + '\'' + '}'; }}}Copy the codeimport org.apache.ibatis.mapping.CacheBuilder; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.springframework.beans.factory.support.BeanDefinitionBuilder; import java.util.Set; public class Test { public static void main(String[] args) { CourseBuilder builder = new CourseBuilder() AddVideo (" ").addNote(" ").addHomework(" "); addName(" ").addPpt (" ").addVideo(" ").addNote(" ").addHomework(" "); System.out.println(builder.build()); StringBuilder sb = new StringBuilder(); sb.append(""); CacheBuilder cacheBuilder = new CacheBuilder(""); cacheBuilder.blocking(false); // cacheBuilder. SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder(); // sqlSessionFactoryBuilder. BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(); // beanDefinitionBuilder.Copy the codeThe chained programming example builds SQL
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
/**
* QueryRule,主要功能用于构造查询条件
*
* @author Tom
*/
public final class QueryRule implements Serializable
{
private static final long serialVersionUID = 1L;
public static final int ASC_ORDER = 101;
public static final int DESC_ORDER = 102;
public static final int LIKE = 1;
public static final int IN = 2;
public static final int NOTIN = 3;
public static final int BETWEEN = 4;
public static final int EQ = 5;
public static final int NOTEQ = 6;
public static final int GT = 7;
public static final int GE = 8;
public static final int LT = 9;
public static final int LE = 10;
public static final int ISNULL = 11;
public static final int ISNOTNULL = 12;
public static final int ISEMPTY = 13;
public static final int ISNOTEMPTY = 14;
public static final int AND = 201;
public static final int OR = 202;
private List<Rule> ruleList = new ArrayList<Rule>();
private List<QueryRule> queryRuleList = new ArrayList<QueryRule>();
private String propertyName;
private QueryRule() {}
private QueryRule(String propertyName) {
this.propertyName = propertyName;
}
public static QueryRule getInstance() {
return new QueryRule();
}
/**
* 添加升序规则
* @param propertyName
* @return
*/
public QueryRule addAscOrder(String propertyName) {
this.ruleList.add(new Rule(ASC_ORDER, propertyName));
return this;
}
/**
* 添加降序规则
* @param propertyName
* @return
*/
public QueryRule addDescOrder(String propertyName) {
this.ruleList.add(new Rule(DESC_ORDER, propertyName));
return this;
}
public QueryRule andIsNull(String propertyName) {
this.ruleList.add(new Rule(ISNULL, propertyName).setAndOr(AND));
return this;
}
public QueryRule andIsNotNull(String propertyName) {
this.ruleList.add(new Rule(ISNOTNULL, propertyName).setAndOr(AND));
return this;
}
public QueryRule andIsEmpty(String propertyName) {
this.ruleList.add(new Rule(ISEMPTY, propertyName).setAndOr(AND));
return this;
}
public QueryRule andIsNotEmpty(String propertyName) {
this.ruleList.add(new Rule(ISNOTEMPTY, propertyName).setAndOr(AND));
return this;
}
public QueryRule andLike(String propertyName, Object value) {
this.ruleList.add(new Rule(LIKE, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule andEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(EQ, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule andBetween(String propertyName, Object... values) {
this.ruleList.add(new Rule(BETWEEN, propertyName, values).setAndOr(AND));
return this;
}
public QueryRule andIn(String propertyName, List<Object> values) {
this.ruleList.add(new Rule(IN, propertyName, new Object[] { values }).setAndOr(AND));
return this;
}
public QueryRule andIn(String propertyName, Object... values) {
this.ruleList.add(new Rule(IN, propertyName, values).setAndOr(AND));
return this;
}
public QueryRule andNotIn(String propertyName, List<Object> values) {
this.ruleList.add(new Rule(NOTIN, propertyName, new Object[] { values }).setAndOr(AND));
return this;
}
public QueryRule orNotIn(String propertyName, Object... values) {
this.ruleList.add(new Rule(NOTIN, propertyName, values).setAndOr(OR));
return this;
}
public QueryRule andNotEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(NOTEQ, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule andGreaterThan(String propertyName, Object value) {
this.ruleList.add(new Rule(GT, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule andGreaterEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(GE, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule andLessThan(String propertyName, Object value) {
this.ruleList.add(new Rule(LT, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule andLessEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(LE, propertyName, new Object[] { value }).setAndOr(AND));
return this;
}
public QueryRule orIsNull(String propertyName) {
this.ruleList.add(new Rule(ISNULL, propertyName).setAndOr(OR));
return this;
}
public QueryRule orIsNotNull(String propertyName) {
this.ruleList.add(new Rule(ISNOTNULL, propertyName).setAndOr(OR));
return this;
}
public QueryRule orIsEmpty(String propertyName) {
this.ruleList.add(new Rule(ISEMPTY, propertyName).setAndOr(OR));
return this;
}
public QueryRule orIsNotEmpty(String propertyName) {
this.ruleList.add(new Rule(ISNOTEMPTY, propertyName).setAndOr(OR));
return this;
}
public QueryRule orLike(String propertyName, Object value) {
this.ruleList.add(new Rule(LIKE, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public QueryRule orEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(EQ, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public QueryRule orBetween(String propertyName, Object... values) {
this.ruleList.add(new Rule(BETWEEN, propertyName, values).setAndOr(OR));
return this;
}
public QueryRule orIn(String propertyName, List<Object> values) {
this.ruleList.add(new Rule(IN, propertyName, new Object[] { values }).setAndOr(OR));
return this;
}
public QueryRule orIn(String propertyName, Object... values) {
this.ruleList.add(new Rule(IN, propertyName, values).setAndOr(OR));
return this;
}
public QueryRule orNotEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(NOTEQ, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public QueryRule orGreaterThan(String propertyName, Object value) {
this.ruleList.add(new Rule(GT, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public QueryRule orGreaterEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(GE, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public QueryRule orLessThan(String propertyName, Object value) {
this.ruleList.add(new Rule(LT, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public QueryRule orLessEqual(String propertyName, Object value) {
this.ruleList.add(new Rule(LE, propertyName, new Object[] { value }).setAndOr(OR));
return this;
}
public List<Rule> getRuleList() {
return this.ruleList;
}
public List<QueryRule> getQueryRuleList() {
return this.queryRuleList;
}
public String getPropertyName() {
return this.propertyName;
}
protected class Rule implements Serializable {
private static final long serialVersionUID = 1L;
private int type; //规则的类型
private String property_name;
private Object[] values;
private int andOr = AND;
public Rule(int paramInt, String paramString) {
this.property_name = paramString;
this.type = paramInt;
}
public Rule(int paramInt, String paramString,
Object[] paramArrayOfObject) {
this.property_name = paramString;
this.values = paramArrayOfObject;
this.type = paramInt;
}
public Rule setAndOr(int andOr){
this.andOr = andOr;
return this;
}
public int getAndOr(){
return this.andOr;
}
public Object[] getValues() {
return this.values;
}
public int getType() {
return this.type;
}
public String getPropertyName() {
return this.property_name;
}
}
}
Copy the code
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.lang.ArrayUtils;
import com.gupaoedu.vip.pattern.builder.sql.QueryRule.Rule;
import org.apache.commons.lang.StringUtils;
/**
* 根据QueryRule自动构建sql语句
* @author
*
*/
public class QueryRuleSqlBuilder {
private int CURR_INDEX = 0; //记录参数所在的位置
private List<String> properties; //保存列名列表
private List<Object> values; //保存参数值列表
private List<Order> orders; //保存排序规则列表
private String whereSql = "";
private String orderSql = "";
private Object [] valueArr = new Object[]{};
private Map<Object,Object> valueMap = new HashMap<Object,Object>();
/**
* 或得查询条件
* @return
*/
private String getWhereSql(){
return this.whereSql;
}
/**
* 获得排序条件
* @return
*/
private String getOrderSql(){
return this.orderSql;
}
/**
* 获得参数值列表
* @return
*/
public Object [] getValues(){
return this.valueArr;
}
/**
* 获取参数列表
* @return
*/
private Map<Object,Object> getValueMap(){
return this.valueMap;
}
/**
* 创建SQL构造器
* @param queryRule
*/
public QueryRuleSqlBuilder(QueryRule queryRule) {
CURR_INDEX = 0;
properties = new ArrayList<String>();
values = new ArrayList<Object>();
orders = new ArrayList<Order>();
for (QueryRule.Rule rule : queryRule.getRuleList()) {
switch (rule.getType()) {
case QueryRule.BETWEEN:
processBetween(rule);
break;
case QueryRule.EQ:
processEqual(rule);
break;
case QueryRule.LIKE:
processLike(rule);
break;
case QueryRule.NOTEQ:
processNotEqual(rule);
break;
case QueryRule.GT:
processGreaterThen(rule);
break;
case QueryRule.GE:
processGreaterEqual(rule);
break;
case QueryRule.LT:
processLessThen(rule);
break;
case QueryRule.LE:
processLessEqual(rule);
break;
case QueryRule.IN:
processIN(rule);
break;
case QueryRule.NOTIN:
processNotIN(rule);
break;
case QueryRule.ISNULL:
processIsNull(rule);
break;
case QueryRule.ISNOTNULL:
processIsNotNull(rule);
break;
case QueryRule.ISEMPTY:
processIsEmpty(rule);
break;
case QueryRule.ISNOTEMPTY:
processIsNotEmpty(rule);
break;
case QueryRule.ASC_ORDER:
processOrder(rule);
break;
case QueryRule.DESC_ORDER:
processOrder(rule);
break;
default:
throw new IllegalArgumentException("type " + rule.getType() + " not supported.");
}
}
//拼装where语句
appendWhereSql();
//拼装排序语句
appendOrderSql();
//拼装参数值
appendValues();
}
/**
* 去掉order
*
* @param sql
* @return
*/
private String removeOrders(String sql) {
Pattern p = Pattern.compile("order\\s*by[\\w|\\W|\\s|\\S]*", Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher(sql);
StringBuffer sb = new StringBuffer();
while (m.find()) {
m.appendReplacement(sb, "");
}
m.appendTail(sb);
return sb.toString();
}
/**
* 去掉select
*
* @param sql
* @return
*/
private String removeSelect(String sql) {
if(sql.toLowerCase().matches("from\\s+")){
int beginPos = sql.toLowerCase().indexOf("from");
return sql.substring(beginPos);
}else{
return sql;
}
}
/**
* 处理like
* @param rule
*/
private void processLike(QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
Object obj = rule.getValues()[0];
if (obj != null) {
String value = obj.toString();
if (!StringUtils.isEmpty(value)) {
value = value.replace('*', '%');
obj = value;
}
}
add(rule.getAndOr(),rule.getPropertyName(),"like","%"+rule.getValues()[0]+"%");
}
/**
* 处理between
* @param rule
*/
private void processBetween(QueryRule.Rule rule) {
if ((ArrayUtils.isEmpty(rule.getValues()))
|| (rule.getValues().length < 2)) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),"","between",rule.getValues()[0],"and");
add(0,"","","",rule.getValues()[1],"");
}
/**
* 处理 =
* @param rule
*/
private void processEqual(QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),"=",rule.getValues()[0]);
}
/**
* 处理 <>
* @param rule
*/
private void processNotEqual(QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),"<>",rule.getValues()[0]);
}
/**
* 处理 >
* @param rule
*/
private void processGreaterThen(
QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),">",rule.getValues()[0]);
}
/**
* 处理>=
* @param rule
*/
private void processGreaterEqual(
QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),">=",rule.getValues()[0]);
}
/**
* 处理<
* @param rule
*/
private void processLessThen(QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),"<",rule.getValues()[0]);
}
/**
* 处理<=
* @param rule
*/
private void processLessEqual(
QueryRule.Rule rule) {
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
add(rule.getAndOr(),rule.getPropertyName(),"<=",rule.getValues()[0]);
}
/**
* 处理 is null
* @param rule
*/
private void processIsNull(QueryRule.Rule rule) {
add(rule.getAndOr(),rule.getPropertyName(),"is null",null);
}
/**
* 处理 is not null
* @param rule
*/
private void processIsNotNull(QueryRule.Rule rule) {
add(rule.getAndOr(),rule.getPropertyName(),"is not null",null);
}
/**
* 处理 <>''
* @param rule
*/
private void processIsNotEmpty(QueryRule.Rule rule) {
add(rule.getAndOr(),rule.getPropertyName(),"<>","''");
}
/**
* 处理 =''
* @param rule
*/
private void processIsEmpty(QueryRule.Rule rule) {
add(rule.getAndOr(),rule.getPropertyName(),"=","''");
}
/**
* 处理in和not in
* @param rule
* @param name
*/
private void inAndNotIn(QueryRule.Rule rule,String name){
if (ArrayUtils.isEmpty(rule.getValues())) {
return;
}
if ((rule.getValues().length == 1) && (rule.getValues()[0] != null)
&& (rule.getValues()[0] instanceof List)) {
List<Object> list = (List) rule.getValues()[0];
if ((list != null) && (list.size() > 0)){
for (int i = 0; i < list.size(); i++) {
if(i == 0 && i == list.size() - 1){
add(rule.getAndOr(),rule.getPropertyName(),"",name + " (",list.get(i),")");
}else if(i == 0 && i < list.size() - 1){
add(rule.getAndOr(),rule.getPropertyName(),"",name + " (",list.get(i),"");
}
if(i > 0 && i < list.size() - 1){
add(0,"",",","",list.get(i),"");
}
if(i == list.size() - 1 && i != 0){
add(0,"",",","",list.get(i),")");
}
}
}
} else {
Object[] list = rule.getValues();
for (int i = 0; i < list.length; i++) {
if(i == 0 && i == list.length - 1){
add(rule.getAndOr(),rule.getPropertyName(),"",name + " (",list[i],")");
}else if(i == 0 && i < list.length - 1){
add(rule.getAndOr(),rule.getPropertyName(),"",name + " (",list[i],"");
}
if(i > 0 && i < list.length - 1){
add(0,"",",","",list[i],"");
}
if(i == list.length - 1 && i != 0){
add(0,"",",","",list[i],")");
}
}
}
}
/**
* 处理 not in
* @param rule
*/
private void processNotIN(QueryRule.Rule rule){
inAndNotIn(rule,"not in");
}
/**
* 处理 in
* @param rule
*/
private void processIN(QueryRule.Rule rule) {
inAndNotIn(rule,"in");
}
/**
* 处理 order by
* @param rule 查询规则
*/
private void processOrder(Rule rule) {
switch (rule.getType()) {
case QueryRule.ASC_ORDER:
// propertyName非空
if (!StringUtils.isEmpty(rule.getPropertyName())) {
orders.add(Order.asc(rule.getPropertyName()));
}
break;
case QueryRule.DESC_ORDER:
// propertyName非空
if (!StringUtils.isEmpty(rule.getPropertyName())) {
orders.add(Order.desc(rule.getPropertyName()));
}
break;
default:
break;
}
}
/**
* 加入到sql查询规则队列
* @param andOr and 或者 or
* @param key 列名
* @param split 列名与值之间的间隔
* @param value 值
*/
private void add(int andOr,String key,String split ,Object value){
add(andOr,key,split,"",value,"");
}
/**
* 加入到sql查询规则队列
* @param andOr and 或则 or
* @param key 列名
* @param split 列名与值之间的间隔
* @param prefix 值前缀
* @param value 值
* @param suffix 值后缀
*/
private void add(int andOr,String key,String split ,String prefix,Object value,String suffix){
String andOrStr = (0 == andOr ? "" :(QueryRule.AND == andOr ? " and " : " or "));
properties.add(CURR_INDEX, andOrStr + key + " " + split + prefix + (null != value ? " ? " : " ") + suffix);
if(null != value){
values.add(CURR_INDEX,value);
CURR_INDEX ++;
}
}
/**
* 拼装 where 语句
*/
private void appendWhereSql(){
StringBuffer whereSql = new StringBuffer();
for (String p : properties) {
whereSql.append(p);
}
this.whereSql = removeSelect(removeOrders(whereSql.toString()));
}
/**
* 拼装排序语句
*/
private void appendOrderSql(){
StringBuffer orderSql = new StringBuffer();
for (int i = 0 ; i < orders.size(); i ++) {
if(i > 0 && i < orders.size()){
orderSql.append(",");
}
orderSql.append(orders.get(i).toString());
}
this.orderSql = removeSelect(removeOrders(orderSql.toString()));
}
/**
* 拼装参数值
*/
private void appendValues(){
Object [] val = new Object[values.size()];
for (int i = 0; i < values.size(); i ++) {
val[i] = values.get(i);
valueMap.put(i, values.get(i));
}
this.valueArr = val;
}
public String builder(String tableName){
String ws = removeFirstAnd(this.getWhereSql());
String whereSql = ("".equals(ws) ? ws : (" where " + ws));
String sql = "select * from " + tableName + whereSql;
Object [] values = this.getValues();
String orderSql = this.getOrderSql();
orderSql = (StringUtils.isEmpty(orderSql) ? " " : (" order by " + orderSql));
sql += orderSql;
return sql;
}
private String removeFirstAnd(String sql){
if(StringUtils.isEmpty(sql)){return sql;}
return sql.trim().toLowerCase().replaceAll("^\\s*and", "") + " ";
}
}
Copy the code/** * SQL Sort component * @author */ public class Order {private Boolean ascending; Private String propertyName; private String propertyName; Public String toString() {return propertyName + "+ (ascending? "asc" : "desc"); } /** * Constructor for Order. */ protected Order(String propertyName, boolean ascending) { this.propertyName = propertyName; this.ascending = ascending; } /** * Ascending order * * @param propertyName * @return Order */ public static Order asc(String propertyName) { return new Order(propertyName, true); } /** * Descending order * * @param propertyName * @return Order */ public static Order desc(String propertyName) { return new Order(propertyName, false); }}Copy the codeimport javax.management.Query; import java.util.Arrays; public class Test { public static void main(String[] args) { QueryRule queryRule = QueryRule.getInstance(); queryRule.addAscOrder("age"); queryRule.andEqual("addr","Changsha"); queryRule.andLike("name","Tom"); QueryRuleSqlBuilder builder = new QueryRuleSqlBuilder(queryRule); System.out.println(builder.builder("t_member")); System.out.println("Params: " + Arrays.toString(builder.getValues())); }}Copy the code