[Java]手动构建SQL语法树（sql简单无嵌套）并输出与之对应的SQL语句之二

package com.hy;// 构建SQL语法树public class Entry { public static void main(String[] args) throws Exception { Node query=new SetNode(" "); query.addChild(new KeywordNode("Select")); Node fields=new SetNode(","); fields.addChild(new ValueNode("name")); fields.addChild(new ValueNode("ismale")); query.addChild(fields); query.addChild(new KeywordNode("From")); Node tables=new SetNode(","); tables.addChild(new ValueNode("userinfo")); query.addChild(tables); query.addChild(new KeywordNode("Where")); Node condistions=new SetNode(" and "); Node ageCompare=new CompareNode(">="); ageCompare.addChild(new ValueNode("age")); ageCompare.addChild(new ValueNode("41")); condistions.addChild(ageCompare); Node levelCompare=new CompareNode("<"); levelCompare.addChild(new ValueNode("level")); levelCompare.addChild(new ValueNode("9")); condistions.addChild(levelCompare); Node likeCompare=new CompareNode(" like "); likeCompare.addChild(new ValueNode("name")); likeCompare.addChild(new ValueNode("'王%'")); condistions.addChild(likeCompare); query.addChild(condistions); query.addChild(new KeywordNode("order by")); Node orders=new SetNode(","); orders.addChild(new ValueNode("sn asc")); orders.addChild(new ValueNode("level desc")); query.addChild(orders); System.out.println(query.getSql()); }}

Select name,ismale From userinfo Where age>=41 and level<9 and name like '王%' order by sn asc,level desc

package com.hy;import java.util.ArrayList;import java.util.List;// 节点抽象类，作为各种节点的基类public abstract class Node { // 此节点的子节点 protected List<Node> children; // 表示此节点的文字 protected String text=""; public Node() { children=new ArrayList<Node>(); } // 添加一个子节点 public Node addChild(Node n) { children.add(n); return this; } // 取得节点在sql中该有的文字 public String getSql() throws Exception{ String retval=this.text+""; for(int i=0;i<children.size();i++) { Node child=children.get(i); retval+=child.getSql(); } return retval; }}

package com.hy;// 关键字节点,比如用来表示SQL中select，from，where，order by等关键字的节点// 此类节点下面没有子节点public class KeywordNode extends Node { public KeywordNode(String keyword) { this.text=keyword; }}

package com.hy;// 值节点,比如用来表示字段，表，条件，数值等节点// 此类节点下面如果存在查询也可能存在多个子节点public class ValueNode extends Node { public ValueNode(String value) { this.text=value; }}

package com.hy;import java.util.ArrayList;import java.util.List;// 集合节点,比如用来表示SQL中字段组，表组，条件组，and组等容纳多个子节点的的节点，整条SQL也是这个节点// 此类节点下面一般有多个子节点，如查询多个字段，从多个表查询，包含多个条件，按多种情况排序等public class SetNode extends Node { // 子节点之间的分隔符 protected String seperator; public SetNode() { seperator=""; } public SetNode(String seperator) { this.seperator=seperator; } public String getSql() throws Exception{ String retval=this.text+""; List<String> ls=new ArrayList<String>(); for(int i=0;i<children.size();i++) { Node child=children.get(i); ls.add(child.getSql()); } retval+=String.join(seperator, ls); return retval; }}

package com.hy;// 比较节点,用来表示条件比较的节点，如age>41,level>9// 此类节点下面理论上存在左右两个节点，如果存在查询也可能存在多个子节点public class CompareNode extends Node { public CompareNode(String value) { this.text=value; } public String getSql() throws Exception{ Node left=getLeftChild(); Node right=getRightChild(); String retval=left.getSql()+this.text+right.getSql()+""; return retval; } private Node getLeftChild() throws Exception { try { return children.get(0); }catch(Exception e) { throw new Exception("No found left node under node'"+this.text+"' "); } } private Node getRightChild() throws Exception { try { return children.get(1); }catch(Exception e) { throw new Exception("No found Right node under node'"+this.text+"' "); } }}